Hi CJ, glad to see you posting!
Well, the answer to your question depends on just how much money you want to spend! As far as the engine goes, pretty much nothing more than an oil change and new plugs, and a carb tune. Unless the bike is hard starting I would not worry about a valve adjustment yet. These engines are pretty much bullet proof and last a long time, like 10 times what you have on it already.
Due to the age, you may want to consider replacing the front springs and flush the shock oil and replace. The same goes for brake and clutch fluid, something that should be done every 4 - 5 years anyway. Same applies to the engine coolant. Inspect your rear shock for leakage and replace the shock if it is leaking. Grease the splines on the driveshaft. Due to age only you may want to consider replacing all wheel bearings, swing arm bearings and neck bearings as with age grease tends to turn into glue.
Inspect vacuum lines and replace any that are hard and brittle. Same goes for coolant hoses. Other than that just ride the puppy and take care of problems if and when they come up...