Road race on the schedule

In order to keep my edge for Marathon Nationals, I'm doing my first road race Sunday. I really have know idea how all the tactics work, other than ride hard, ride smart, and stay upright. It's also a local race down in Harlingen, Return of the ride the ride to no where. It'll be 50 miles, that is sure to be pretty much all out, so I'll need to stay in the group as much as possible. The training schedule is on as planned, no tapering whatsoever, which means I'll be on the mtb for 3hrs Sat. as scheduled. No worries though, if I suck Sunday, then I suck. But I'm going to work my ass off in order to be ready for Nats.