There so much to know that I would buy the Caravan and Motorhome Club touring guide of France. It gives so much information we found the guide invaluable even when we were experienced. It also contains details of a lot of sites too including municipals. Non members can buy one for small extra fee.
My main advice would be to use good caravan and car recovery service in case anything goes pear shaped. We used CMHC Red Pennant for vehicles and travel insurance as it is a one stop shop with an excellent reputation.
Enjoy your venture
www.caravanclub.co.uk