Although, I haven't been, yet... I think I can help you.
Yes, there are a lot of different trails, and there will be groups that go out, based on vehicle capabilities and drive experience. Ergo, you will be able to pick the appropriate group. You already mentioned a tire upgrade, no one would argue with that!
As far as doing all three days... I think that there will be a few people that only run the weekend days. I don't think there would be a problem with that.
The only other recommendation that I would make would be for you to remove the stock step rails, even if just for that weekend.
Feel free to swing over to
www.ecxc.com for more information.
-Jeremy