indysteel gave you good advice. What you get at the SAG stops "should" be adequate, but since you know nothing about the ride and the site doesn't tell you much, it might be wise to stash a half of a peanut butter sandwich in your jersey and/or a banana and/or fig newtons. These are all good fuel for endurance riding. But, yeah, if you have money on you, you can always stop somewhere and buy food. Keep it to things that are easily digestible, so your body doesn't have to use it's energy resources to digest instead of fuel your legs. Several small meals/snacks are definitely better than one big one. Protein and carbs are the main staples on an endurance ride ... plus hydration.

I have a feeling you'll be pleasantly surprised that you won't be the last one's. Riders of all levels typically do these rides. Try to find other riders that are going about your pace and team up with them. Draft with them and then do your share of pulling (as long as you are comfortable with this and they don't seem to mind). My friend and I did a metric century a couple of months ago where we buddied up with two guys going our pace. We got behind them a little before a SAG stop. When we got to the stop, we thanked them for pulling us and told them we'd be happy to do our share if we ended up riding with them more. They were very friendly and we did the rest of the ride with them. It made the whole experience really great to have that added camaraderie and support. Not to mention the pulling, which we did help with.

We then did a full century a month later, which our husbands did with us. My husband, the strongest rider, pulled us pretty much the entire way. We went much faster than we would have without him, since we never had to pull, and doing it together, again, made it a great experience.

So, whether or not you ride with your husband, try to hook up with some other people that seem to be going your pace. Sometimes you'll hang with a group for a while, and then lose them at a SAG or somewhere else. But then you find others. You may not become buddies with them, but most people on these rides are pretty social and friendly.

Every organized ride I have done has had a route map. I rarely have to look at it, though, if ever, because you generally just follow the people in front of you. Often times there are markings, like painted arrows on the ground, or signs posted. You start getting used to looking for them after a while. If ever you start to wonder if you are on the right path, you can stop and look at your route sheet. Mine is usually folded up in the back of my jersey. Some people do have tricky devices to keep there's on their handlebars for easy reference. Just follow one of THEM!

Lastly, if the idea of completing a full 100 miles is freaking you out, just focus on the SAG stops. I make a point of knowing how many miles it is to the next one and that is my focus. Before you know it, you're at the last SAG stop and only have one last "leg" to go. I just look at my route sheet before leaving the previous stop to know at what mile the next one is. If you have a bike computer, you can keep track of miles.

Good luck! I'm sure you're going to do great.