The basic mods which will give you better performance and wont cost all that much are:
1. Open air filter.
2. Larger intake pipe.
3. Larger exhaust. (remove catalytic converter or gut it out)
4. Air Flow Meter modification.
I think after all that it tends to get tricky and more cost is involved. You'll have to look into a Turbo kit. Bare in mind these older engines weren't designed for turbo's and adding one could be potentially disastrous later on. Not only that, you'll be looking at thousands of dollars just to get it done...not worth it really when you could just buy an already turbo'ed engine and drop that in.
A lot of performance enhancements comes from maintenance. The first step would be to check everything that's in your engine right now and make sure nothing is at fault and everything is running at it's optimal level.
To adjust the timing you'll need a special Timing Light. You plug it up to the battery and the first spark plug wire. Start the engine up and point the light at the crank. There is a timing mark on it. Adjusting that mark is done by loosening the Distributor Housing Bolt and moving the Distributor. Depending on how you move it, it will change the timing.
Kind of hard to explain, but I hope that helps.