Step 2 · Access the Plumbing
Remove the faucet handles, typically held by a set screw, and the surrounding trim plates (escutcheons). Unscrew the shower arm and head. Since we're assuming no rear access panel, you must create an opening from the front. Use a utility knife to score the grout around the tiles you need to remove. An oscillating multi-tool with a grout removal blade is ideal for this. Carefully cut an opening in the tile and backer board large enough to access the valve and surrounding pipes, usually around 12x12 inches centered on the valve body. Always wear safety glasses and a dust mask during cutting.