Don't have one in the shower and after a hot experience or two, my wife insists
that I replace the old style with a pressure balanced model.

I can cut and solder copper pipe pretty well, but is replacing the valve inside
a shower wall a job for a plumber?

There isn't much room in the wall after removing the front plate, and the other
side of the wall is a tiled bathroom also.

I was thinking that if I have to remove some tiles, (and break them) I could add
a matching style in a different color and make it look like it was done on
purpose.