Turn off the main water supply
Open the shower faucet to drain remaining water
Remove the shower handle
Remove the trim plate and any screws
Inspect the valve type and replacement part
Cut or remove access to the valve if needed
Disconnect the old valve from the supply lines
Remove the old valve from the wall
Install the new valve in the same orientation
Secure the new valve to framing or mounting brackets
Reconnect the water supply lines
Solder, glue, or tighten fittings as required
Install the new trim plate and handle
Turn the water supply back on
Check for leaks
Test hot and cold water flow
Seal any wall opening and repair the wall if needed