Solvang was my first century too, a few years ago. It's lovely and very moderate, an excellent choice.
I usually ate too much on centuries when I first started out. Don't eat a grand slam or a breakfast burrito unless that's what you always do before a big ride. Eat small amounts frequently. Don't overeat the night before or your pre-ride nerves are going to send you to the loo multiple times.
You should try to eat and drink the way you always do on longer rides - don't try something new on the century day. Eat LIGHTLY at the stops - don't think of it as a feeding free-for-all - just eat a small amount of something you know agrees with you. You can grab something and put it in your pocket to eat in between stops if you want, too, just as insurance. I usually do this end end up with all that food still in my pockets at the end of the day.
I hated Spiz on the one ride they had it - but I think mostly it was the name. I wouldn't really like to say what that word reminds me of. ;D
Sleep is important - try to sleep the night before.
Also, try to go out slowly and warm up -- better a longer time at the finish than to blow up in the first 40 miles and suffer the whole rest of the day. Pick a MPH for yourself you know is a little too easy, and force yourself to stay under that for the first 30 miles or so. Or if you use a heart rate monitor, pick an easy HR and stay under it.
Have fun!