Im almost 52yo and have had project cars since I was 14yo, and the most important thing I learned was if you have a project car, It is best to have TWO cars so you can drive one while you are working on the other car.
When you work on your project car, and it is your only car and go to work on it, and think, "oh, this will only take a few hours" WRONG!!! Sh!# happens! Like, new parts are wrong or dont fit, broken bolts, dont have all the tools,
have to go to the parts store for something you overlooked, ect. I am not saying it cant be done with just one car, it is just 10x more convenient with two, or at least have access to another car at a moments notice. The last thing you want to have to do when
working on your project car, is have to rush to return it drivable again.
As far as mods for your 2004 Prix, you could add a factory supercharger! I think that would give you the best bang for the buck. It was available for the 2004 Grand Prix from the factory, Im sure you know this already.
Happy wrench turning on your endeavors!