As for advice, build up the pace (occasionally get crashed shortly after a new owner!), and use the wealth of information on here. The Wiki is good, and search is your friend. They are phenomenal cars.
No. I bought my GTO3 from new in May 2003 and the cars were supplied with the 5 speed box only. 3r's came out a few months later and the 6 speed was offered as an option on these.