Pulled a 37 ft 5th wheel 2500 miles to and from glacier national park this summer with a gasser. We never had trouble finding a station to get in and out of for fuel. I did pass up one and look for a different, but that only happened one time. The pilot truck stops I stopped at had straight drive through lanes for gas and diesel so it was really nice. I had the same concerns as you when planning the trip. But it wasn't an issue.
I did trade my gasser after the trip for a diesel though. I loved my gas truck, still miss it. Id much rather have a gasser. But Wind, Long Hills, and 12,500+ lb 5th wheel doesn't make for a comfortable tow. The hills i was find, wind I was ok. But the 2 combined, It was very hard on the truck, and me. To much shifting. The truck had the power to do it. But I was manually shifting it too often and playing the coast up and accelerate down game the whole time on narrow roads that I didn't want to have to do that again. Coming from a gas guy, if you can afford the Diesel buy it. It wasn't a mistake me buying the gas truck, because I didn't want a diesel at the time and still don't. But I had to find out for myself. If I were just staying in Minnesota the gas truck is all I need. But for traveling long distances like we plan to do now. The diesel was necessary.