Has a bad oil leak a few people have said its the seal is it hard to fix?

If the spark plug is oil fouled, you either have leaking valve seals, or bad piston rings. Bad rings would be accompanied by excessive blow-by. With the engine running, remove your oil filler cap. If there is air pulsing out of the filler tube, it your rings. If not, it is your valve seals.

Have the entire engine pressure washed and have light sensitive dye installed in the crankcase and use a black light to locate the source of the leak after you have driven it a few days..

I'm assuming "white" smoke and not "black" since you didn't mention.
If white smoke, it's coolant or oil leaking into the cylinder heads while it is not running.
If oil and from leaking valve guide seals, it's not a serious thing and basically a nuisance. Just keep your motor oil level topped off until you have new seals installed or dispose of vehicle.
If coolant, it's a much more serious problem. The liquid in the head will do two things. One, foul the spark plug and possibly cause hydraulic lock (fluids cannot be compressed and cylinder locks up)
Check you oil level and if keeps going down a quart every few hundred miles, it's the valve seals.
Check your coolant. If down, it's possibly a head gasket leak, which is not uncommon for vintage and make.
If coolant keeps going down and not leaking on ground, that's a smoking gun, not to make a bad pun, for a leaking head gasket. At this point, it's prudent to first invest $10 on Barr's Leak Copper (looks like liquid copper in a jar) and add to your coolant system. Follow manufacturer's instructions and then see if problem either persists or abates.
If it abates, go and buy a lottery ticket since you're very lucky and solved a serious problem with an inexpensive fix.

Good Luck

The Chrysler minivan products all had leaking problems. I have had 5 or 6 different Dodge or Plymouth minivans from 88 to 99. How bad is it. The most common thing is Valve cover leaks. Front and rear seals in the engine leak as well as the oil pan gasket. If its leaking a little bit at a time open the hood and look at the front and rear of the engine. Do you see grease and oil that has gone down the sides of the engine? Do you see a lot of grease on the engine with some clean streaks going through it. You may be able to see where its leaking from. If you know someone that knows what their doing have them change the leaky gasket/s. If not you can probably have it repaired for less than buying another van unless other things are seriously wrong with the van.
Hope this helps... Dale

is the leak visually on the ground, then it seems like you could get under car and wipe a few things and see what leaks, thats a big leak, car would be leaving a smoke screen behind you from getting all over exhaust system. I would have to say, REAR MAIN SEAL BETWEEN MOTOR AND TRANS, OIL FILTER NOT TIGHT, Is oil all over the timing belt? front gasket/seal failure, Oil sending unit, is the light on or pressure gauge work?

the crankshaft seal or the oil pan gasket?

Usually, there is a seal between the engine and transmission that goes bad. There are a lot of seals that hold oil in the transmission. The most common problems are the front transmission seal or the axle seals. If it is a big leak it shouldn't be hard to find.

Sounds like the oil cooler is leaking. That is what the oil filter actually threads into. If so, that is not too bad to replace. Other oil leaks/seals to look out for are tail shaft seal (back of trans), rear axle seals, and vavle cover gaskets on top of heads. I would recomend checking the rest of the car carefully for any other leaks. Parts are typically cheap, but labor can get expensive to get to leaking seals and replace them.

If You Had replaced The Seal After That Also Oil Leakage Is Occur, Then It Is a Problem Of BAck Compression Please Check It. thanks.

Not common, part is cheap, fix is easy. You will need a few basic hand tools a metal punch awl to remove old seal (like an ice pick) and soft faced hammer to drive the new seal in.