In reply to dartfrog: Unless you're the nervous type you'll probably be alright just turning up at a campsite, all the ones I've been to over the years are pretty large and are rarely pushed for space. On a related note, Campin les Prez in Grez-sur-loing is a nice site, pretty big with good facilities and very reasonably priced. It also has a very nice river that is lovely to swim in on a summers evening.
Guidebooks: if you can get your hands on it Essential Fontainebleau will cover your needs, it's currently out of print though. Failing that, 5+6 and 7+8 are good for individual problems, the new white circuit book is pretty good for circuits. Avoid the old purple circuits book.