Ditto on what everyone else said. You may also may want to consider taking Road 101 from Cycle U. It is $35 and for me it went a long way toward making me more comfortable riding with groups & in a paceline (something you'll really want to take advantage of on STP). Also, in the past, local REI's have hosted free classroom sessions about STP. You'll get some good tips there. Since you live in Auburn, if you aren't hung up on completing every single mile and don't have to worry about having your bags transported for you, Just pick up the route near home. You'll avoid those first chaotic miles and be able to get the butterflies out. Enjoy the journey...and that includes all of the training leading up to the event.