Interior Cabinets

Lots of good information on www.generalfinishes.com then click videos.General Finishes is the best and easiest product I've used and you can call them for advice.

I don't have any connection with GeneralFinishes other than using their products.

There is a product called Howard's Restore-A-Finish. It's sold at the big-box stores. When applied, it softens the old finish, adds in some stain colorant, and hardens to a new finish. Most folks are amazed at the transformation.
It will not work on a polyurethane finish but most RV's have a lacquer or oil finish when new.

After the stain, use Minwax Satin Wipe on Polyurethane. A very light sanding between coats (like 320 paper). Wipe off sanding dust (I use naptha) prior to following poly coat. Prior to the poly, if you have any spots that need color consider using a felt tip pen and wipe it to blend it. Can get color matching pens at art store.