It would depend on the quality of the existing paint or clear coat. If it's chipped or has a powdery surface, you might be better off having it repainted. There have been a lot of advances in paints over the last ten years, but the EPA has cracked down on some of the best ones.
There are paints out there that are used on airplanes that can withstand huge changes in temperature and can protect a plane going 400 mph against chipping. The paint cost hundreds of dollars a gallon. There are other paints that are pretty cheap, but chip easily and don't do well in the sun. In the end it's going to come down to the people you hire to do the work and how much you're willing to spend. 50% of the job is in the prep work. If you don't properly prep the RV, even a good paint job will look bad and won't last.