We are putting new tile on our tub surround. We have the cement board installed and will soon do the tiling. I need to replace the bath hardware, which I thought would be relatively straightforward, and maybe it is. But a lot of the hardware I'm looking at is more than the basic stuff we had, with temp controls, anti-scald, etc., which appears to require more work -- maybe behind the drywall -- than just basicaly slipping the new hardware on. But I'm not sure. I want something simple to install. Here is a photo what is on there now. Will I need to remove this and cut a larger hole in the board to get behind it, or is there a fixture that won't require that? I'm looking at HD. Thanks much.