Plan ahead! I always fill up before I hook up the car at home. I usually scout out for fuel when I'm out from the campground to see what's the best place to go and if too tight I have DW follow me. I fuel up, then pull to the side and hook up the vehicle, usually there's a shopping center nearby.
On most interstates the gas stations and truck stops near the exits are usually very simple to get into. I can't back up either so if I was desperate and couldn't make it to another place I'd just pull to the side and release the car. I haven't needed to do this because I've been able to get fuel in the places I've stopped. One thing for sure to remember, the exits that are close to town shopping areas, most of these gas stations are not set up for long vehicles.
I invested in Microsoft's Streets & Trips software with the GPS. There are plenty of add-ons where you can add every Shell or EXXON or Flying J stations in the country. They show up along the route and include phone numbers etc. You can plan your route and call ahead just to check out their set up.
Street & Trips with GPS
Definitely have a spotter because you're not the only one there and some people get in a big hurry and will zip right around you at the last second as you want to move.