The good news is that most haven't played in the Greyhawk realm so it will all be new. The other good news is that I rarely ever stay to the "campaigns" created for each world. What I like to do is give objectives that the group picks from and they evolve with the party instead of filtering a group through a pre-constructed adventure from A-Z.
Here are some great links to help you learn more about the world of Greyhawk.
Greyhawk Gods
Greyhawk Locations
Greyhawk Site
Legends of Greyhawk
Try and stay with the 3.0 and 3.5 rules but if you see something you like I am flexible
[ July 03, 2004, 04:10: Message edited by: Cyclop ]