Darrell - please don't worry - you'll have a great time. Just take some time to really plan your route before you set off, even if you are using SatNav. The service areas off autoroutes are no problem, even for the largest van - and there are always the specialist HGV pumps which are often used by large outfits. Everything is more geared up to caravanning than in England - there are proper areas to park, with plenty of room, and often picnic facilities (tables, litter bins, etc) nearby.
Another way to remember the correct side when you're driving is 'keep your bum in the gutter' and this will ensure you go the correct way around roundabouts, pulling out of petrol stations, etc). Honestly, towing in France is a pleasure compared to England - and as said, if you travel on a Sunday the roads are empty of HGVs apart from refrigerated ones.
The autoroutes in France are mainly toll - you can pay with an English credit card, but some tolls are very small so keep some small change handy in your car. Take a ticket from the booth on entering the autoroute, and on exiting, or at various points on route, hand in the toll ticket and the price comes up on a notice on the toll booth. The passenger nearly always has to pay the toll, but sometimes there are 'English' booths where you can pay on the driver's side. Some areas around major towns are free, some you have to pay a couple of euros.
On viamichelin you can put in your 'preferences' for the route - so if you've an overnight stop planned somewhere you can enter that as a 'via' and it will calculate you a route with the overnight stop planned. It will also tell you approximate driving time, tolls, etc. You may find it's also worth having a paper map (michelin road atlas for France is great) just in case anything goes wrong with the technology.
Take the tip in one of the above postings, and always fill up in supermarket petrol stations (once you don't have the van with you - ie on site, and when sightseeing) but use the autoroute petrol stations on the journey there and back, it's easier. Make sure you have a warning triangle, first aid kit, and high-vis vest with you, as these are legal requirements. Also you may need to adjust your headlights, either electronically or with blackout tape, for driving on the wrong side. Watch out for police on junctions - they're often there to make sure you stop at the STOP sign, and you'll have an instant fine if you don't. There's a great posting on the uk campsite website (http://www.ukcampsite.co.uk/chatter/display_forum_topics.asp?ForumID=7) for first timers in France. Hope you have a great time, and if there's anything else you need to know I'm sure there's someone here who can help.