And then without the trimmings:
When we were looking at some of the replacement pieces at Lowe's tonight... There didn't seem to be anything that would've fit. Screw hole to screw hole is 3", and the length of the cartridge (I think that's what I've seen it called around here anyways) is like 1" out to the base.
Obviously replacement shower panels are on the list too. The only downside is that the shower is open at the back (it only has a 1/3 wall on it, enough to cover the end of the tub and that is it) - so complete tub surround kits won't work. Is plain paneling the next best/easiest thing? We're not really interesting in doing tiles or anything complicated.
Any help, guidance, and/or suggestions would be appreciated. I would love to tackle this project myself, but am also willing to call in a professional if it requires it (such as, replacing the piece that regulates how much and how hot/cold of water is coming out).