I have a 1997 porche
Gravity does all the hard work. If you can figure out how to work a wrench, you can change your own oil. I'd pickup a repair manual, it will have the basics that tell you how to do a tune up/oil change etc.
You should also google Porsche groups, I'm sure there are a lot of greasemonkeys hanging out there who love to train noobies.
Its not difficult, but you need to make sure you have the right filter, and know where the drain plug is, before you get started.
Basically you drive the car a bit to get the oil warm, then you park it and set the brake. Put a drain pan under the oil pan near the drain plug. Unscrew the drain plug, wear rubber gloves, the oil will be hot, let the oil drain into the pan, now fish around in the pan for the drain plug that you dropped into the hot oil cause the oil was burning your fingers, when you find the drain plug, clean it off with a paper towel and open a beer. Now you need to remove the old oil filter, they usually either unscrew or are in a cannister, that service manual I told you to buy will tell you where it is and how to remove it. now open another beer, and put the clean filter in wherever the old filter came out of. Best to order a pizza now or you'll be drunk by the time you get this job done.
Okay clean filter is on, time to put the drain plug back in the oil pan, if its an aluminum pan, you probably should use a torque wrench to make sure you don't overtighten it and strip the threads, otherwise just put a new lock washer/crush washer on the plug (it should come with the filter)
Now add some quarts of your favorite oil after opening one more beer. That manual you bought will tell you exactly how many quarts of oil your engine will hold.
After its all together, check the dispstick to make sure you have enough oil in your car, then start the engine and move the car, look underneath for oil leaks, thats a sign that the drain plug isn't tight enough.
Take it for a test drive as soon as you sober up from all the beer. Easy peasy.