Good luck, and enjoy yourself!
If you use a HRM you can use that to 'ride in the zone', but otherwise, over 10 miles you really have to go hard if you want a good time. Chris Boardman, and the equally esteemed Brahan both suggest slightly easing back or going steady to start with, then really going for it. Also, do a warm up riding the entire course, which will get your body ready, and get you familiar with the undulations and wind.