The best bit of advice I can give is....buy my one, click the link below, own the legend that is 666DAN
http://www.skylinesaustralia.com/forums/t180592.html
On another note, having owned 2 x R34's check the following things-
Have they got splitfires (the stock packs *will* die, this is ~$500 cost)
Check for underbody rusting from floods or seaside life in Japan
Check the engine fault codes running the ECU diagnostic on the cars you look at (take a paperclip)
Sniff the radiator for signs of blown headgaskets
Check turbo condition, they die easily on R34's (ask if it's had a highflow job with steel wheels)
Do a basic check of all the normal car things
R34's however have very few other design faults so you should be able to find a good one
Welcome!!!