[folivier]

I just looked on Newell's website and Nichols RV & Truck is listed as a preferred service center. That being said I think I would talk with Newell and relate this experience with them. I'm sure they would want to know of your experiences and might want to review this place. And they may be willing to act as a go between. They could also recommend one of the other preferred service centers nearby.
Good luck.