All good advice in this thread. I did STP for the first time last year - and did it in one day.

I would add that you should experiment with different food/drink types WELL before the stp. Preferably you should ensure that you (and your stomach) are comfortable with the food/drink you'll use while doing some longer rides (50+ miles.) I made the mistake of trying a completely new type of energy drink the week before STP. Halfway through the ride I had some serious GI issues - fortunately they resolved after I dumped the offending sports drink. So, I would have all of that worked out before you ride.

Good luck, you have plenty of time to get into riding shape if you start training now.