I do not know much about older imprezas. I own a 2002 wrx.

I wouldnt recommend buying an 02-03 wrx unless you want to do a tranny swap they are like glass . 04+ Have much better trannys. As for buying one do what any normal car buyer would do test drive to see if you like them. Take it to a trusted mechanic subaru is prob the best place to take it to will cost some money but worth it.