I assume you are talking about Tactical Handgun 101? Which one?
Don't wait too long to register -- they always fill up. And yes, you will get a detailed e-mail with what to bring once you register. I can't find my e-mail or I would have sent it to you now. Tell me which class exactly and I will give you a better idea what you need.
As for the gun -- I struggled with this as well. I asked Randy before the class and he said -- bring what you carry. Now... that being said... I can't see you getting the most benefit out of the class with a really small gun -- i.e., a Guardian G-380. Same with the R-9... I am not sure I would put my gun through that -- i.e., 600 or so rounds, dropping mags in the dirt, etc.
I took the class with a 9mm SP-101 and I was very happy with it. Granted, I had the added speed of the moonclips, but I kept up just fine. I did not feel like I missed out on anything. The only part of the class that didn't really apply was the malfunction clearance session -- and Randy actually loaned me a 1911 for that part so I would have something to do. Randy is very knowledgeable with revolvers, so wheelguns are not a problem.
Now... that being said... Randy is from the Gunsite school of thought and lost of people there will have full-size 1911s. The rest will probably have Glocks. You will take some good natured ribbing in the nature of-- why can't you carry a real gun, etc.
At one point we did a drill where you had to shoot two plates, speed load, and shoot two more plates. Two people went at the same time and whoever finished first was the winner. I beat the guy I was up against who was shooting a full-size 1911 -- because I hit every plate with the first shot.
In the end, I think I earned a lot of respect for getting through the class and keeping up with "just" an SP-101!