I live in Portland and my partner lives in Vancouver WA. We discovered an RV repair place near his house, tucked away on a side street: RV Pro (Welcome To RV PRO, Inc!
You can see the sign from I-5, near the 78th Street exit in the Couve. For major body work we take our 16ft DWR Airstream to George Sutton in Eugene, but this RV Pro place does work on Airstreams and they have an accessories room jam-packed with everything you might need. A nice little shop!