ah yes the treuno/levin ....yup they are good drift cars. if you get one you really do want an AE-86 (Hachi-roku) unless your willing to do all the work to make an 85 comparable. they are becoming very hard to find nowadays.
upgrades are cheap and easy....many choices for your motor swap depending on what your needs are. the most populaur be the high-comp motor swap. maybe $400-$800 for the motor, do the work yourself...easy.
the hardest thing about them is parts more for looks, aero-kits, that kind of stuff. and nice looking wheels hard to find and expensive. go to
http://www.club4ag.com very nice site with lots of info. here's one of our trueno's RIP