The free online NADA is worth exactly what you pay for it. If you get the subscription version of Kelly or NADA, it has some value because it is based on market data. Banks, credit unions, RV dealers and some public libraries have paid subscriptions and might give you a look. Or you can buy your own copy - NADA sells theirs via their website.
You should also be aware that private sales prices are generally well below what dealers ask. I suggest that you look on a site such as PPL Motorhomes that reports the actual selling price of their consignment sales transactions. That will tell you what real buyers paid for real RVs in the past two years.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL