2004 3295RK Shower Question

[Mark7]

I have an old Montana 3295RK I am constantly tinkering with, and one of the improvements I want to make is to install a real shower valve!

I have owned 5 - 5ers in the last 20 years, and this is the first one that has had no access to the back side of the shower plumbing. It is against a cabinet in the LR right by the entry door. There are no removable access panels.

Can those valves be removed / serviced from the front side?

On another note... we conserve water when we shower by shutting off the flow at the shower head rather than closing both valves. When it's rinse time there is always an ice cold stream of water for a few seconds (not bad when it's expected) and that is why I want a single handle valve like a Moen so that we can remedy that issue.

That phenomena has happened in every camper I have owned. Can anyone explain why that happens?