I did replace the Shower Head in my 22M, but not the Hot & Cold valves. It seems that they must be serviceable from inside the shower, because I do not see how you could access them from the exterior wall. As your 22R is just four years old, I am curious as to the reason for their replacement. Here are my performance measurements for my new Shower Head: http://www.winnieowners.com/forums/f...er-354104.html
The shower facets have not failed at this time. But I did want a plan in mind for when they do. I usually upgrade kitchen and bath sink facets from the cheap plastic RV style to residential units.
All facet sets I've ever worked on have threaded nuts on the bottom/back side of the facet to secure them to the mounting surface. I think you have to open the side panel next to the sink to gain a narrow access path or cut a big section of shower wall out to service those valves.
Fred & Denise (RVM157) New Mexico
2007 Excel Classic 30RSO & 2015 Mini Winnie 22R
2007 RAM 3500, Diesel, 6Spd Auto, SWD, 4x4, CC & LB