Welcome!
Here's my take on modding one of these platforms...
1. Brakes *Make sure the thing can stop and handle the project you are getting into!
2. Milzy's Engine and Trans Mounts *The instant difference makes this the first mod I would recommend after the brakes are done.
3. Exhaust *Even just a down pipe to start. The bottle neck of a downpipe is one of the first things to get rid of, if you are going to really get into an engine build then this is the time to just throw the headers in and do the exhaust front to back
4. First tune time *A tune at this point I would highly recommend, the car has been through enough changes now that a tune will actually net you some very impressive gains
5. Suspension *Take a inch or an inch and a half off it along with some new struts and it will blow you away the difference in the ride and handling.
6. Decision time, Engine or Body... If you are going all out, and going to build yourself a 300hp 3400, then now is the time to contact the builders out there and get into head and cam package. If you are happy with the performance you have at this point then I would go the body route. Rims, tires, body kit, stereo and so on.
There is a massive amount of info on your car now around here, anything you are getting into this is the place to go over it with the guys that are in the know... good luck with the build and happy modding!!!