The classifieds here on IRV2 would be good. I would also list it on RVTrader.com, and you may want to select their option of advertising it until it sells!
One caution on Craigslist (and any other list for that matter). Unless you personally know the buyer, tell them that you will only accept a direct transfer of funds between their bank and yours! DO NOT accept money orders or cashiers checks!
When I advertised a 5th wheel on Craigslist, I got two or three scam e-mails a week!
Good luck, happy trails, and God bless!