I had a problem with the elevation the last time in CO (about 6 years ago). Since we're going to NM later this month, I've been reading up on it. Of course, most of the websites are about very high elevation, but most of it still applies.
Don't do too much on your first 24 hours there, and don't sleep in the day time if you can help it. You need time for your body to adjust to the oxygen content of the air, and when you sleep your respiration goes down and slows the process.
If you develop symptoms (headache, nausea, fatigue), go ahead and rest (it's the only thing you'll feel like doing), but try not to sleep. Yes, hydrate like you said. If you have to go to a higher elevation for some reason, don't go until your symptoms are gone, because they will only get worse.
I hope you'll be there a day or two before the race, so you can adjust. It happened to me after a 15 hour bus ride (I was on a group ski trip) during which I could barely move my legs, so I think that was an extenuating circumstance. On other trips to CO I had no problems. As an athlete, I'll bet you're less likely to have problems adjusting.
Good luck at the event!
Karen