Problems, pricing, opinions

So i bought this 98 VW Passat 20V Turbo, off some people my dad knows from the town he works in.

Started off pretty nice, but after a few months i've been experiencing alot of the same problems i'm reading about.

-Car jolts at times comming to a stop
-Oil leaking/burning smelling up the car
-Acceleration Hesitation
-Gas doesn't seem to last long what so ever.

When i first got it, i actually planned on dropping some cash in the body, rims, lowering it (free, but still planned on taking time to do it) new color, new seats/lights all that nonsence. But i'm starting to have second thoughts.

I plan on getting new spark plugs just for the sake to get new ones in there. Adjusting the timing, and a new gas filter.

What else should i do besides dumping the ideas and the car?

And what would it cost to get the transmission inverted. It's automatic now, but i'm too familiar with standard.

There's plenty to go wrong, but when they run right they're nice to drive. If the check engine light is on have someone familiar with VW scan it (I'd get it scanned anyway if the car isn't running well). Tou need a VW scanner or simulator like VAG-COM to do the job right. Changing to a manual would be very costly & require a complete parts car.