My dishwasher was not getting the dishes clean, so i started taking the lower end apart to clean, got to a gray wheel looking object with a screw in the top which was recessed and still the wheel looking object will not come off, it will spin but will not come off, I need to finish taking it off because I dropped a screw down in the bottom area where the water settles.

Using a light lubricant, you might place a drop or two of oil on the upper rack's rail wheels or the bottom if either squeaks when pulled out. Take a look at the wheels on each rack (up and lower) to see if either is damaged or is not rolling properly on the rails. There's nothing to explain the "scum" other than the water coming into the machine....Cascade is a good brand and a minimal amount is needed for each load. The CUP located in the door of most machines will hold about twice what's required to clean a load of dishes,pans,etc. Cascade has a RINSE AGENT included in its manufacture. Be sure to rinse your dishes well before loading. Try different settings and see if it makes a difference.
If you have the time, take the lower rack completely out, when the machine is cold and the water has been pumped out of the chamber. With your fingers, feel around the bottom-center, check for debris, forks or other objects that can sometimes collect under the lower plate and under the drying element.
There's little to speak of, dishwashers are merely "boxes with spinning hoses and a drying element" so any liquid "coming-into" the wash-cycle is a function of your local water supply and plumbing. Sometimes "hard" water causes a "scum" and people will use softeners which are installed outside and will "clarify" water before inputting into your house. That would be a last resort.

Usually this is a contanimation issue, check and clean all drain filters, look for particulate matter in the spray ports, Usually you have to take the whole thing apart and clean debris.

Took apart again and found the stepping motor which diverts the water from lower to upper spray arms to be burnt out. I was able to manually set the diverter to the correct position so the dishwasher works but I am waiting for new parts to properly repair the problem.

Is water also standing in the bottom like it isn't getting pumped out? If so, probably the drain system is plugged and everything below the lower spray arm needs to disassembled to the deck--noting the position of each piece as they are removed. Look for food plugging holes in the deck and any obviously damaged parts. Clean the large screen in vinegar and hot water--let soak for a while to remove water and food deposits. Check the drain hose from end to end looking for kinks or other restrictions. Make sure the pump mechanism at the bottom turns freely. Check both spray arms for plugged spray holes or split seams. Reassemble in reverse order. Run a cycle without dishes to clean further--make sure the water drains out at the end. Listen for proper water movement while running. Open the door to inspect progress several times.

Without a model number, or even a brand / manufacturer, it is nearly impossible to tell you how your product comes apart. Many brands have a screw (often times with left hand threads) holding the spray arm on, while others may come off by just lifting on the spray arm while turning it CCW, or might have locking clips which need to be released.
In any case, before going that far, go to a hardware, appliance parts, or possibly grocery store to find a product called Dishwasher Magic. It is in a small rectangular bottle. Use that as directed in a cycle to clean out your dishwasher. The spray arms may need to be cleaned out of blockage from candy wrapers, toothpicks, seeds, etc., or possibly even replaced if unable to fully clean out. Also, dishwashers will not clean very well if you are using hard water. I'd suggest looking into installing a water softener.

Hold the lower spray arm hub (plastic bolt spray arm connects to) and turn the lower spray arm counter clockwise to remove it.
Using a torx bit, remove the 4 screws and the top cover. Remove the screws for the lower cover and the chopper cover. Insert a flat screwdriver it into the clip of the chopper cover to pull it up easier.
Unless there are alot of "foreign objects" in that area, be prepared to replace the chopper, the motor and/or sump assembly.

Look in the inside for any screen that would be easily removed, some dishwashers have a self cleaning filter so you may not find it. I have a lot of other tips for you if your dishwasher is not cleaning so check it out.
http://tclaundryrepair.com/dishwasher

How do I take apart and clean the filter, I've gotten the screws out but to do now?

I would suggest calling whirlpool to have a tech come out and look at it. Your appliance is still under warranty if it is under 1 yr old. It will cover parts and labor.

These instructions will work for almost any GUxxx series whirlpool dishwasher:

You probably don't have enough pressure from the pump. That's most likely caused by a clogged filter. So start by checking the filters- the easy one to get to is located behind the chopper in the base of the dishwasher. Grab the whiteish tube going from the bottom of the dishwasher towards the back of the dishwasher and get it to spin about 1/8th turn clockwise and then pull up. If that part works out for you, you'll see four torx screws. Don't loose any of these, they cost $6 each. Take out all four and pull the round white thing up and set it aside. You'll see gray plastic now. Towards the front, down inside, you'll find two more torx screws that are smaller than the first four. Take those out and get the two gray pieces they hold down out of your way. The flat one will come out easily, the other one will take some persistence. Once you get that out, you can see the smaller filter behind the chopper. It sits inside a thin groove, pay attention to this groove, as you'll want to put it back in the wrong place if you don't look it over before you take it out. Remove the filter and chopper assembly and clean it off if it's a mess. Then put the thing back together the same way you took it apart.

If this fixes your dishwasher, then you know pressure was your problem. If the problem reappears and you follow these steps again only to find the filter full of food again, then your chopper isn't chopping anymore. This is probably because the end of your impeller is broken off and isn't engaging the chopper anymore. If that's the case, replace the impeller (about $20 new).

To replace the impeller:

SHUT OFF THE ELECTRICITY to the dishwasher and unhook the wires in the electrical connection box. Notice that (hopefully) the white wire connects to a white wire and the black wire connects to the black wire and the green or bare wire wraps around a screw. You'll need to reconnect this back properly when you're finished with everything else.

Disconnect the drain line, either at your garbage disposal or at the dishwasher if you can get to that connection. Watch out for water, it'll go everywhere when you pull this loose.

Turn off the source of water, if you don't have a valve under your sink for this (you'll wish you did) then you'll need to shut off the water to your house. Disconnect the water supply line from the
dishwasher, this connection is underneath the dishwasher opposite the electrical connection box.

Pull the dishwasher out and flip it over 45 or 90 degrees, your choice.

Unscrew the capacitor from the motor assembly (it's the round looking thing with two wires mounted to the motor), but leave the wires connected to it. Put the nut back on the bolt so you don't loose it. This makes getting the thing out easier.

Find the drain pump, it has a plastic tube connected to it. There is one torx screw holding that in. Take the screw off, pull the tube and the white thing with wires out, leave its wires attached. Your model may not have wires here.

Pull the wire connector off the motor. Remember where it went. Pull the two wires off the thermistor, they should be Yellow (with a black stripe) and white. Make a note that these two wires go on the thermistor so you get them back in the right place. Pull the Blue and gray wires off the drain pump. Make a note that these go on the drain pump so you get them back in the right place.

Next, there are three tabs that you need to find and pull out. They are little L-shaped wedges that hold the round gray assembly to the dishwasher. They are located about 1/3rd of the way around the circle, so once you find one, the other two are pretty easy to locate. Do not loose these parts.

Once you get those pulled out, the entire gray assembly can come out.

Look behind the motor for a bolt. Get your socket set out and find a 3/8ths socket. Put that on an extension, and the extension on your ratchet. Slide the socket between the white plastic protector and the grey plastic (it's a tight fit) and take out the bolt. Do not loose the bolt. Leave it in the plastic so you'll remember to put the plastic back. Grab the motor and turn it about 1/8 to 1/4 turn (it will only turn one direction) and then pull it out of its housing.

From here you can access the second filter, the one that isn't so easy to get to. It's probably fine. And now you can see the impeller, it's white and black and attached to the end of the motor shaft.

To remove the impeller, stick a screwdriver into the back of the motor, being careful not to damage the windings. Hold the screwdriver with one hand, grab the impeller with the other hand and unscrew it from the motor shaft.

Install new impeller on the end of the motor shaft, make sure it's tight.

Reverse instructions to put it all back together. Make sure you get the thermistor and drain pump wires connected correctly. White/Yellow to thermistor (little round dodad) and blue/gray to the pump (big thing on the gray part that drains water from the tub.)

Don't forget to re-attach the drain and supply lines, turn on water and check for leaks. Fix leaks. You may need Teflon tape, depending on the type of supply connection you had to undo. If you use plex tubing and connectors, you don't need Teflon.

Do NOT turn back on the electricity until the dishwasher is completely wired back up, closed, secure, and don't forget the ground (bare or green) wire around that screw.

I'm not responsible if you follow these instructions and end up shocking or killing yourself or your dishwasher. This is what worked for me.