I think you'll need to do some reading up here. The list is long. These are extremely reliable overall, but they are luxury vehicles and at 200,000 miles and 20 years old there are a lot of wear items that might be due. Bushings, CV boots (or axles), driveshafts, engine pulley bearings, heater tees, fluids, muffler, etc...
Just start with the basics.
Depends on how you need the car, too. If you need this to get to work and school, go on dates, etc... then having a reasonably reliable ride is more enjoyable than a lifted rig with 10 different worn out parts ready to leave you stranded somewhere. If this is purely for fun and you don't need to get to work/school then you can afford to be more focused on the fun stuff, haha.