Wotcha and welcome - If you go for a car that is all running but needs attention - which should be possible with the budget Gambit suggested, you will be able to conduct a full refurbishment of everything and learn as you go and also get a taste of teh good stuff before you start taking things apart. If you get a car with major issues to start with you can end up chasing your tail for ages.
We have threads on here about full engine rebuilds (Savage + Tlag) and also some on the drive improvements (Bazza + Rollomite) there are many other examples of members doing great stuff to their cars in the project section.
I dont think any of the Subaru technology incl turbos are out of your capability.
They are as cheap or expensive as you want to make them but modding is addictive so beware ;)