Those sound like some crazy high prices.
I'm contemplating painting the end caps on the 5th wheel but I have done it on a boat.
If it's just the front end cap, it should be a quick and easy process with the possible exception of removing the old logo.
There is not need to remove the old gelcoat. It needs to be cleaned and de-waxed and then a light sand with a fine grit so the paint has some tooth to grab onto. If there are any chips or cracks, now is the time to fix them but otherwise, it's a pretty simple there isn't much to get in the way and no need to remove. Any auto body shop should be able to do it but you may want to consider marine paints as they are designed to work with fiberglass.
The rear is likely to be a little more complicated as there are likely windows and ladders to work around but still nothing particularly difficult.
Assuming you have a compressor and the spray guns, I would say $200 for materials maybe less. An auto body shop maybe $500. (assuming you remove the logo and other vinyl graphics.