Welcome to the boards!
Most of this information can be found either on
www.g20.net or do a search in the forums.
As far as those mods go, here are some sites you can do some browsing around on also...
www.nopi.com for interior stuff/suspension/etc.
www.digitalracer.com for pretty much anything and everything
www.tires.com for wheels/tires
www.tirerack.com for wheels/tires/suspension
www.stillen.com for suspension/interior/front aero kit/etc.
as far as tires, i'd look for some 195/60 instead of the 195/65, the 195/60's come stock on a 1999-2001 g20 "t", the smaller sidewall would increase your handling capabilities by a margin, check
www.tirerack.com for that size tire, they'll have reviews, test and surveys on the different model tires, good luck
