I've done a few marathons and endurance events, but this will be my first XC race.
The website doesn't seem very well laid out to me. I'm sure I read somewhere that there were different numbers of laps for the different classes, I can't find it now.
Looking at this page, http://www.xcracer.com/jn_raceentry/viewevent.php?event_id=78 most of us will be in one race.
How long and how wide is the course ? Mass starting elite women, veteran men and 12 year olds on a short single track course doesn't sound ideal.
Are there plenty of overtaking opportunities ?
Are the starts staggered ?

Start times are staggered, usually a minute between categories. They're usually done pretty well to avoid too much unnecessary overtaking. If you're at the front of one of the later categories, or at the back of an early one expect to do some overtaking/be overtaken.

Remember that many of those categories will likely only have 2-3 people in, it's not going to be 1000 riders going off together.

Laps will vary, generally it's something like:

Elite: 5
Expert/Master: 4
Sport/open/vet/grand vet: 3
Fun: 2

With women usually one less than that.

Course will have a wide start, then into normal singletrack, there will be intermediate bits of fireroad to overtake. If you're behind someone much faster, calling 'on your right/left' is accepted protocol, if someone shouts it to you and it's possible to move over then do so if it's safe/appropriate.

Laps will be about 25-30 minutes for your average racer, top elites will get closer to 20, some people will be much slower.

And have fun.

Thanks, njee, the staggered starts are a relief. I could just imagine a group of 12 year olds getting all excited and racing off at the start, then getting in the way as everyone who had paced themselves a bit better caught them up.
I'm familiar with the practice of shouting "On your right/left". I ride 12 hours solo, so I've heard it a few times. 🙂