Replacing brake calipers

I had a similar problem with my Winnie....sat for almost two years on grass, and the brakes rusted to the point that when I took it down for an annual state inspection, I couldn't go over 45 mph!!
It cost me over $2K for the brakes to be completely replaced. I looked at the parts, and maybe they could have been turned, but the time and effort pretty much offset the cost of replacing with new. I also have less than 30K miles on the MH.

Now, I take the RV out every month, run the genset, and drive about 5-10 miles, if we don't take it out camping. That was an expensive lesson, that I don't want to repeat!!

If I was you, I would probably have the front brakes repaired.....then take the MH out and test drive it. You REALLY want all your brakes working properly, so test to see that it has stopping power. You can always go back and have the rear brakes done at a later date.
Best to find a Mechanic/Shop that you trust, or that friends trust. It's easy to get ripped off.:(

Ask whomever is going to do the job, if they'd mind returning the rotors and calipers to you AS THEY ARE REMOVED from the vehicle...

You would have to be there waiting as the parts were removed.

If someone is trying to pull the wool over your eyes, your making of a request like the above will make their hair stand out on end. If the service manager tries to give you any flak over your request, move on down the line.

This is not the same as asking that the old parts be returned as you pick up the vehicle. It is specifically a request for them to bring the parts to you as they are removed. It costs them nothing to bow to your request. Let's see what they say. Call it contriving your own B.S. Detector.

The vehicle may have been sitting long enough for the slides on the front rotors to become rusted to the point they would not slide.
I normally do the caliper and brake pad changes my self. The slides must be coated with good brake lube not just grease. The slide area would need to be cleaned, wire brushed heavily on first change. The factory does not lube very good.
CALIPERS DO NOT GET TURNED, the rotors get turned
Rotors can be turned if they have not been done before. Replacements can be cost effective. I can get rotors turned for about 1/2 the cost of replacements.
The system needs to be totaly flushed and new brake fluid installed. Make sure the fluid is high temperature not just regular brake fluid.
You may want to get a second estimate.

I was told that the front calipers were worn and could not be turned. I pointed out that the RV only has 22K miles and was told the rotors were rusted, pitted and the one with the stuck caliper was warped.

I agree, just do the fronts. As you suspected there is no connection to the fronts.

I would just do the fronts. Also replace front hoses and full system fluid flush.

What is wrong with the front rotors? Usually only replaced when too thin to turn them true one more time. If you had no pulsing brake pedle then thickness is the only reason to replace. I don't know the cost but sometimes a new rotor is only a few dollars more than turning the old stuff.