Fort Ord right? I believe I was one ahead of you, I'm Cesar. Don't sweat it. First couple of CX races will be tough when your a newbie. During my first one (DFL at Candlestick) I pretty much raced w/ all racers (A/B/Masters/Men/Women). I got OBLITERATED. My buddy, who got me into this d*&n CX thing, even lapped me on the 2nd to last lap. Technique and practice helps a lot. Practice mounts/dismounts, run ups and carries. Don't worry about the bunny hops. I only saw a few MTBers able to do that this weekend, mostly because they had front susp. I dismounted along side an MTBer on one of the logs and I mounted and kept pace w/ him by running.
I've also found that race-specific conditioning helps. While one may be able to do a century, it's a different story mainting 90% HR for 30 minutes straight. Practices rides should be as close to race conditions as possible, in order to acclimate yourself to riding when your lungs are about to explode.
Don't be discouraged, it's tough but fun. Put it this way, I've pretty much raced all season, and I was 3rd from last, even with 5 laps... Sadly, I've only really completed the full laps at one race, Surf City. And I ride twice a week, cyclops twice a week and run 1 or 2 times. My problem is getting myself to traing at 90% HR, I get lazy. And at this point in the season, most experienced riders are already at peak conditioning.
There's still a few races left. Next week at Fort Ord, Pilarcitos (2), EBCX on 12/19, and CCCX in Jan.