1. If I were you, I'd run 125D and the Unlimited Rookie class. They both will probably have 20-30 riders.
2. Gates open at 6:30 Saturday morning, signup starts at 7:00, practice starts at 9:00. It would be much more relaxed if you follow us up and camp out Friday night, though. You can sign up Friday evening from 7:00 - 9:00 and them sleep in Saturday. I'll be doing hamburgers on the grill Friday night and coffee Saturday morning.
There will be 10 - 12 practice sessions. If you sign up for two classes, you will get two practice sessions. Maybe #3 for 125D and #7 for Unl. Rookie (3 and 7 just used for illustrative purposes. They will have the practice schedule posted when you sign up).
They they run 20 or so qualifier motos. They call them qualifiers because (even though everyone qualifies) the results from the qualifier are used for gate pick in the main event. The main counts for everything so a last in the qualifier and a first in the main is a first. They usually run 3 lap qualifiers and 5 lap main events.
Not likely for those two classes (since they are the largest), but if they run multiple classes in the same moto, they might do a staggered start. By that I mean, they might drop the gate and let the +35 riders go, then reset the gate, and then let the +25 riders go.
3. I would shoot for 6:30 Saturday morning so you're not rushed. Ideally, I'd aim for 8:00 Friday night.