When you say its not worth it , why exactly do you say this? I'm not looking to get high HP or anything like that. Just want to make it a little more enjoyable to drive.
How much would you actually say "its too much money" to dump into making a p5 turbo?
On top of whatusername said, you're going to need new, stronger internals, because if you run boost on your stock P5 FS-DE engine, it'll turn into a Zoom zoom boom. There isn't a massive aftermarket performance catalogue for our cars, so you're going to run into a lot of little and some big bugs that if you don't know how to do it, or aren't very knowledgable on engines, you'll be paying a shop a lot of money to do. Even then though, if you turbo'd your car, your going to have to take it in to get tuned so you get peak performance, and hopefully it wont blow apart on the dyno. For $3500, I could find an older model (94-01) subaru impreza, maybe even a WRX, and right off the bat I have a car that has a much vaster array of performance options, as well, i'm making a lot more torque and HP stock than my P5.
To me personally, I think turboing a P5 is a bad investment, but everyone has a different opinion, and reason as to why they want to do it, or have done it, and thus view it differently. If you want to make your car more exciting to drive, take it to a track one day, it's always more fun to drive a slow car fast, than a fast car slow anyways.
If you really have an itch to mod it for performance, look into a KL series swap, if you have the mechanical know how, it wont be as harsh on your wallet, and it's a little less of a headache.