Is there any legal compensation for a RV that is sold as new but already has over 2000 miles on it?

First, did you purchase the RV from a dealership or an individual? Dealerships have what they call "demo" models that are "new" vehicles, but they have driven for test drives, ect. The documents you signed at the time of purchase should reflect this and list the mileage. However, if you purchased the RV from an individual different laws may apply. Contact your local DMV for guidance. Did you notice the mileage and ask questions prior to purchasing the RV. The only reason I would think that the mileage issue would be unknown is if you purchased it sight unseen.