Here's my experience of an MSV day at cadwell in the Zed:
http://www.350z-uk.com/forum/viewtopic.php?f=36&t=46957&hilit=+cadwell
If you're averagely enthusiastic, you'll probably only manage about half a dozen laps on standard discs and pads, so allow plenty of cooldown time. If you have or can get some uprated pads beforehand, do so.
Other than what the other guys said, build up speed slowly and have fun, Cadwell is a fantastic track.