I had my 74 Boler
painted at a auto body shop 20 years ago for $1,000.
There was several spots that required fiberglass repair, including a broken front window and a bunch of cracks (several feet long) in the fiberglass on one side of the window and extending onto the roof (it looked like the previous owner backed into the window with a flat bed truck).
They used a single stage polyurethane automotive paint
It turned out great and I have been very happy with the staying power of the paint
over the last two decades.
I would suspect the price may be a bit higher now!
If I was to paint a camper again, I would definitely go to a body shop.