Let us know how it goes! I'm also a total newbie with racing (seems like most people start out when they're really young) and I'm looking forward to learning from your mistakes.
Just remember no one's there to judge you and all the most embarrassing mistakes have already been made. If you fall over in tricky stuff, just do it properly with your feet on the pegs and your head up and over the handlebars. Don't kick your bike over when mounting by not throwing your leg quite high enough over the seat - you'd be surprised what mistakes you make when you're tired/sore/nervous. Let's not get into how I know that one.