We just took off the four tiles surrounding the valve, replaced it, and replaced them. It does require being able to get more of your tile, or being okay with an accent tile there. But it works, even if it’s not ideal—it isn’t an area that gets much direct water in most showers.

Do note that you don’t need to change the valve just to use a different shower head, though—only if you’re changing out the trim. If your valve otherwise works you might look at other trim options that will fit first. You can still use your preferred shower head.

I was thinking the same thing as artemis78 - why do you need to change the shower valve in order to change your shower head? Certain types of mixing valves allow you to change the trim of your valve (example, Brizio and Delta). You could update the trim for your mixing valve without the need to get into your wall.

Some mixing valves are able to be changed simply by removing the escutcheon plate that is behind the rest of the trim kit. For example:

In order to provide you will helpful advice, you need to explain what the reason is for needing to change the mixing valve in order to change your shower head - because you can use any shower head with any mixing valve - except in certain circumstances.

For example, if you wanted to add something like this:

The above is a Grohe shower bar where the mixing valve controls + shower head + hand held shower head are all one piece. You would need to have compatible Grohe mixing valve in order to install one of these.

This next one is also made by Grohe - it is supposed to be a retro fit shower bar - it might be able to be used with your current mixing valve:

"Can we retile one wall in the shower or do we need to retile the entire shower?"

Yes. The Tile Council of North America allows the installation of tile over tile. Your exposed edge detail will be tricky.

Our house was built in the 70s - every plumber and our contractor has said that a new valve is needed. Good to know that we take out tile and then reseal the small area.

Thank you.

Well, maybe the valve is leaking or something - and can't just be fixed.