Buying a new transmission?

So I have a Honda ex(si clone) with a b18c1 motor and it has the civic tranny. I'm saving up cause I wanna buy the gsr tranny which is the same type as the motor. Would i have to buy anything apart from the transmission so it can work with the car? And what's a good website where I can buy this transmission at? Please no eBay type websites

Try this: This is the one I've used and trust:
http://www.jdmtigerjapanese.com/honda-acura/transmission-only.html