Be glad it's not at Antietam anymore. The track there was brutal.
Anyways just get good sleep and start mega hydrating the week before the race. Limit yourself to one cuppa joe a day for that week if you can and load a good bit of carbs for two days prior. If you've the time go out and ride for two hours straight as much as possible so you have some idea of what it entails. I'd take a couple of Advil or other NSAID before the event and have some available for after. That takes care of you.
Make sure the bike is up to the job. Do a complete service/checkover and fit a new rear tire if it's even close. Riding for two hours if ya can will also give you an idea of how much fuel you'll use.
When someone comes up behind you yelling and revving the engine let 'em by ASAP. They're not being dicks they're in it to win and you're in the way.
Maybe I oughta go dig up the YZ from West Virginia and run this. Haven't done it since..............I don't remember.