If you can work your very hardest to stick with the group (thus drafting at high speed) you will suffer much less. If you get dropped, try to regroup with others and work with them (rotating paceline, hopefully they will know how to do this, you'd be surprised how many don't). Expect the unexpected! Have fun! Practice( gently) bumping into other cyclists and (gently)touching wheels on grass before you do this race. Don't yell, yipe or scream during the race, unless something very,very,very bad has happened. (this all may sound silly, but it's all from my recent experience as a cat 4 racer). Have fun! (oh, and get in a good warm up on your trainer right before the race of course)