Right, so if you don't already have a USAC license ($60/year) then you pay the $10 daily rate onsite, in addition to the entry fee. That makes you a cat 5 for men, cat 4 for women, for the day.
As a 5 or 4, you can ride in the Bickel, or the Men 4/5. I'm pretty sure the 40+ is men cat 1-4 only; that's a very fast field.
AFAIK, the turn-around is staffed with a volunteer to stop traffic and is usually a cone in the road.