First off, don't try and sell it now. If you want to sell, sell it in the spring when everybody wants to buy a camper. Right now the only people looking to buy campers are people not in a hurry and looking to get a good deal because someone needs to sell a camper now.
Secondly, always private sale for max dollar, no matter what you're selling (car/camper/boat). It's more work though.
Third, you'll likely take a big hit. We bought our 2015 in June of 2018. I'm not certain if they bought it $24k or the MSRP was $24k, but we paid $13k for it. If they paid $24k for it, then it lost half its value in 3 years. And they had stored it inside, used it only a handful of weekends, and everything was in perfect condition. RVs just do not hold value.