I agree with Sheldon.
Don't do anything new on race day. Don't adjust your frames the night before, don't wear a new kind of sock, don't drink some superduper sports drink you haven't tried, etc. And, make sure you do whatever you need to do to get your morning poop done before you hit the course.
I think you'll have a great time. Races are lots of fun, even if you finish an hour after the first finishers.