my Newmar

I would not be happy after seeing this as well. To me, the dealer let it sit too long after the RV delivery with road salt on the chassis. When,or if, they washed the chassis, it appears weeks had already gone by. The dealer should at least cover the cost of a professional rust prevention procedure, possibly a few times over the warranty period. You are currently not a happy Newmar customer, Newmar should at least suggest the dealer cover this cost, or maybe they even share the cost with the dealer. You are both Newmar's & the dealer's customer and have been a good customer for Newmar after owning several other Newmar RV's.
This is what is used to protect the large highway salt trucks in our area from road salt damage:
http://www.rustcheck.com/
I have it applied to my vehicles.
I don't see a locations in your city(only Duluth) , but there are locations is some other northern states.