I did this for my first race last year- what a blast!!! I only wish I could do it again this year. I raced in the support race (beginner), which was cool. I think any age can race the Beginner class. "C" would have been fine also. If I hadn't gone off the side of a steep trail, I might have even trophied!!! Or not, I sure remember being fast ;)
Yeah, they start you one at a time (way less intimidating). The trails were very well marked (it is Hollister, afterall), and there were plenty of flaggers on the trail to warn of any dangerous sections. Last year it was at the upper ranch (very nice trails up there), but it's at the lower ranch this year? Have no fear, those trails are plenty easy. I couldn't believe it when they waived me off after my last lap. I had hardly even broken a sweat. Don't worry about numbers- they assign you one on a peice of paper that you tape to your front plate, and a bar code for your helmet.
Most important thing to remember- Have fun. Don't be scared or nervous, everybody at the event was so friendly. I even met a fellow DRN'er there (angryjim). He's easy to spot- long black hair under a cueball helmet, riding a KTM.
Good luck!!! And don't forget to give us a report! :)