My wife and I just bought a house, and the one area we're not really renovating is the guest bathroom. Unfortunately, the tub is leaking and it looks like we need to replace the cartridge inside the valve. We'd replace the entire valve, but the wall is a solid surface and our contractor doesn't think they could get in there to replace it without cutting a larger hole (which we might not be able to cover easily. So, I've got two questions:

1: Do you, more experienced folks, agree that it'd be almost impossible for a plumber to replace the entire valve without opening up the solid surface wall?

2: Any help trying to identify the model of the cartridge to see if we can get a replacement? The most data I can pull is that the place says "Delta Scald Guard", and the back of the plate has the following model (or serial) number on it: M 3495-04 R1

My googling seems that some of the "Scald Guard" product lines us an RP1991 cartridge, any idea if that would universally apply to this whole product line? (photos below). I've e-mail Delta support as well to see if they can help.

Thanks!

I can’t seem to find an easy lookup for handles this old. Any ideas how to figure out what I need before tackling the project?

My home was built in 1994 and the shower/tub trim kit I'd like to replace is original (see pic). I thought that it was a 1500 series so I bought RP32104 cartridge from Delta and a 1700 series trim kit T17430-SS. However, when I went to take the old unit apart I noticed the trim ring screw holes were both at the bottom at roughly 5 and 7 o clock as opposed to 1 and 7 o clock on the new one. My question is can I find a compatible trim ring with the screw holes at the bottom and use the rest of what I bought, or is everything incompatible with the rough-in that's currently installed?