Hayley, Cascade has a suggested mileage plan for training for STP, right here:
http://www.cascadebicycleclub.com/Ea...tp_mileage.cfm
You don't have to follow it exactly but it doesn't hurt to try to get close. If you train, you'll be fine and it really can be lots of fun. The other recommendation I have is, leave EARLY, as early as you can. It helps keep you out of the big crowd at least at the beginning, before people start spreading out.
"My predominant feeling is one of gratitude. I have loved and been loved;I have been given much and I have given something in return...Above all, I have been a sentient being, a thinking animal, on this beautiful planet, and that in itself has been an enormous privilege and an adventure." O. Sacks