What now? Have my route mapped out...

Don't let the little things spoil the BIG things.

Sounds like you got a handle on things, so now come the hardest part . . .

WAITING.

Relax...you aren't going to be traveling to and camping on the Moon.

A little of the unknown and unplanned is part of the RVing adventure.
You will figure it out and be just fine.
Enjoy your trip.

I have never had problems finding gas stations that will accommodate my rig, 30TT and Silverado TV, some 50ft long total. Don't over complicate tings. While good planning is wise, over thinking details is over kill. Gas stations that are on corners are the best bet usually. Just don't go getting yourself stuck where you have to back out onto the street to get out. If that happens, oh well, its not the end of the world and traffic will stop when you get the back end out in the road. you wouldn't be the first one to have to do this. If you have a smart phone get the RVPARKY app. It has all the Wally worlds and Pilot gas stations and other info on it. Handy app to have.

Stick to the outside lanes at the pumps.

Invest in the book "The Next Exit".

Experience is the best teacher. I've logged well over 100k miles in motorhomes & I preplan everything as much as possible. Biggest concern for gassing up in a gas coach is maneuverability when towing a dinghy. You aren't, so you can back up. Look for the easiest lane to get in and out of - usually the outside - & not necessarily the shortest. Most important thing though is take your time. When driving. When gassing up. Take your time. And always, always get out & look for yourself and use a spotter to help direct you into places where anything could be hit. Enjoy this first trip & it will not be your last.

A class C can fit on any public road so don't worry about narrow roads.

Take your time at a gas station and you will have no problems.

Take your smart phone, tablet or whatever internet device you use. You want a Wally World near Stone Mountain SP? Go to Google maps and type in Walmarts near Stone Mountain SP. TA DA!!! Instant information. Or whatever. We use our tablet constantly when on the road searching for this or that, even making campsite reservations. Get to camp and off it goes! Crickets and birds make a much more pleasing sound.

Where are you beginning and where are you going? Some mountain roads you do not want to be on. Perhaps we can help.

Fuel for your size RV should not be a problem. Don't pull too close to the pump. You need to make allowance for wide turns to get out. As soon as you pull in, if you can, stop for a minute and look the place over. You don't want to get trapped by that convenience store parking in front of the pumps. Look over your escape route.

If you think you'll need WalMart, go to one of their stores now and pick up their road atlas. It will list all the WalMarts.

It sounds like you've done your homework. Relax and enjoy the trip!

I use GasBuddy to find the best price and do not worry about getting in/out and I'm 42'. There are two parts of your trip that concern me in a rental RV... not the RV but a new RV driver. 441 in the Great Smokey Mountains is a long climb up and then a long downhill. Going up you can probably let the tranny do it's own thing (shift out of OD) BUT going down you need to manually gear it down into 2nd or maybe 3rd gear so the engine does the braking, not the brakes. You should be able to go for 30 seconds without using the brakes and then if necessary, put them on fairly hard but briefly to slow back down.
By the time you get back east of Asheville on I-40 you should have no problem with going down Old Fort mountain in a low enough gear.
If you zoom in enough on your map it will show WalMarts or Redbox... Walmart.
Relax... enjoy your trip.

Go to Walmart and purchase a Walmart Atlas. Has all the Walmarts listed and where they have fuel.