As far as how to sell, here are some things that may or may not help...
Clean the trailer well and remove personal items from the cabinets and closets.
Take a lot of pictures showing the exterior from several angles and the interior layout and features. Make sure lighting is good and the background isn't cluttered. A little bit of "staging" is good, just don't go overboard.
Make sure all paperwork is in order and in your name. A bill of sale is a good idea and may be required in some places.
This site and the other I linked are good places to post your ad along with local Craigslist. Look at other ads to identify well-written examples. Include 6-10 of your best photos.
Guard your personal information. On this site, for example, private messages can be used to exchange contact information. It's a good idea to set up an e-mail account just for the sale and close it afterward.
Once ads are posted, be available.
Decide whether you will hold the trailer for a buyer coming from far away. You don't have to- "first cash takes it" is the norm. But if you do, set a clear time limit.
I'd make sure at least one other person is around when people come to inspect the trailer. Have it plugged into power and the fridge turned on and cooled down. If you can connect to water or fill the tank and show that plumbing and hot water are working, even better.
Plan for the secure exchange of a large amount of cash. If your bank has a branch nearby, that would be the place to do it.
And beware of ne'er-do-wells and outright scammers with sob stories and unusual payment requests.
Unless you're in a hurry to sell don't worry as Scamp fifth wheels always sell. A good place to start is to look at the Scamp web sight and see what they go for new and how long the wait is when ordering.