I lived in Denver, and have ridden Vail many times. Are you doing the triple-bypass?
The problem with Vail and Colorado is the air is dry as well, so you will dehydrate much faster. The key is to get there about 5 days in advance, and let your body acclimate to the dryer climate. You may want to stay in the foothills for a few days, and ride the red-rock trail near Morrison, White river ranch, climb Mt. Powell in the gore range outside of vail near piney lake( Do this in a day for 15-20 miles, and 13,500 feet elevation). Awsome climb this time of year. Vail is at like 8,000 feet. Give yourself 5 days if possible. Also is it a team 24 hour race? I may know of a team that is lookign for two more members. PM me if you need any beta.