Gas stations that are part of highway / interstate rest stops should be fine for larger vehicles. I tow a trailer, and many times when I have to get off the highway to fuel up I will watch for gas stations checking out how to get in and out of them... if I see one on my side of the road with easy access, I just pull in. If it is on the other side, I look for a parking lot to pull into and then turn around to head back to the gas station. Ideally a parking lot for a shopping center that has a traffic light at the entrance is best - big parking lot, and a traffic light to get me back on the road.
Since you say "RV is 25ft overall" I am assuming it is a Class C or Motorhome. Check what the overall height is and keep that on a sticky note on the dashboard. You should be fine on most roads, but keep your eyes out for the signs that you probably have always ignored when driving a car - "Bridge ahead 12ft" or whatever height is listed. You most likely will not have any problems with height, just keep it in mind. Speaking of gas stations - the vast majority I've see have the roofs over the pumps well high enough to be above all but the very largest vehicles, you shouldn't have a problem with that.
If you pull in somewhere and find you need to back out blocking a road, get a spotter if you can to guide you and/or stop traffic. Otherwise sometimes you need to sort of creep into the road until someone stops to let you out. Be careful and be patient.
Not long after you get used to driving the rig, you will be fine, and have fun camping!
