Gassing Up

Since you aren't towing a car yet, just stop at most any old gas station that has a little clearance and a canopy (if any) that is sufficiently high. If you need to use a spotter and very slow speeds to safely maneuver or back up, that's fine; most people won't mind (though they may be clueless about what you're attempting to do).

I can think of exactly one gas station I've encountered with my 32' class C that I would not consider stopping at. Somewhat annoyingly, it happens to be a tight little corner station in my hometown that almost always has the best prices in the area...but c'est la vie.

Once you get your car being towed, you'll probably have enough experience to feel a little more comfortable. It will be a bit tougher and require a bit more forethought since you can't back up with a towed car connected (unless you for some reason have a flatbed trailer to tow it with, and even then it's tricky), so you'll need to give a bit of thought to an exit strategy before stopping, but it's really not all that much of a hardship with a bit of practice and a bit of experience.

Edit: I guess I'm late to the party. Whoops. It seems the original poster has things under control by now.