Jason,
I have been to several and set them up as well... They will come in with a small dozer and make a couple small hills, mogules, off-camber stuff, etc...
You will either drive your H2 or a GM owned vehicle provided for the event.
If done well, it will really show off the capabilities of the H2 without going too far from home. I'll try to dig up some photos...
Travis
http://www.HummerTeam.com