As for the NYC Century, the routes are pretty well marked, but there are so many people (especially on the 35-mile route) that you'll probably never even have a chance to get lost.

I'd just make sure your shorts are comfortable for at least one longish ride before the main event. I also have a pair of PI Ultrasensors, but something about the chamois doesn't agree with me; I'd hate to have discovered that on a long ride.