When I did my first century in June I followed the advice of our BF friends.
1. Carb load beginning a couple of days prior to the ride. Don't over do it, but like HOG-I said, pasta seems to be the norm.
2. Begin hydrating a couple of days prior as well. Don't wait until you are thirsty. Drink loads of water.
3. Oatmeal and a banana for breakfast the day of the ride. Great Call! That is what I had.
4. During the ride snack, snack, snack. I used Cliff bars. About 1/2 of one per hour. I found in my training that any more than that caused an upset stomach.
5. 2 bottles. 1 with water and one with sports drink. The sports drink is important to keep your electrolytes in balance. It also helps with the hydration process.
6. I stopped consuming solid foods after the 70 mile point. Switched to Cliff shots, sports drink and water. After 70 miles I really wasn't interested in eating solid foods. Not sure why.
I had only done one Metric Century prior to doing my Full Century. However, I am a "hard-core" bicycle commuter. I had well over 1000 miles under my belt for the year prior to doing the ride.
Oh, I did my metric and full centuries on my 1978 Raleigh Gran Prix 10 speed! You should have an easier time on something a bit newer.
EDIT: Almost forgot. Your mental preparations are just as important as your physical preparations. That is a long time to be in the saddle. On my century, the first 40 miles was into a stiff headwind. Between 80-90 was also back into that wind. Also, it was in mountainous terrain. Such a combination can cause serious mental issues while on the ride. It is amazing how one's demons can come out at the worst possible moment.
Good luck!