Before you begin, completely shut off the water supply to your shower. Locate the shut-off valves, typically near the shower or on the main water line. Turn the valves clockwise to stop the flow of both hot and cold water. Double-check that the water is off by turning on a nearby faucet.

Carefully remove the old shower handle(s) and escutcheon plate. You may need a screwdriver to remove screws or a putty knife to gently pry off any glued or sealed components. Penetrating oil can help loosen corroded parts. Take photos before disassembling to assist with reassembly.

Install the new shower valve, following the manufacturer's instructions precisely. Use new Teflon tape on all threaded connections to ensure a watertight seal. For some valves, soldering may be required; consult your valve's instructions. Securely attach the new valve according to the manufacturer's specifications.

Install the new shower handle(s), escutcheon plate, showerhead, and tub spout. Slowly turn the water supply back on, checking carefully for any leaks around the valve and connections. Adjust the temperature if needed. If leaks persist, carefully re-check all connections and tighten as necessary.