1. Turn off the water at the water main or wherever it enters the house.
2. Cover the tub/shower drain with a cloth to prevent small parts from dropping into the drainpipe.
3. Use a pocketknife to pry off the small round index cover from the shower’s hot-water faucet handle.
4. Remove the screw holding the handle in place, then pull the handle free of the valve stem.
5. By hand, unscrew and remove the escutcheon to expose the stem.
6. Use a valve socket and pliers to loosen and remove the old stem from the wall.
7. Unthread the existing seat from inside the valve with a seat wrench.
8. Brush pipe-thread sealant onto the threaded end of the new stem seat.
9. Use the seat wrench to tighten the new stem seat into the valve.
10. Carefully hand-tighten the new valve stem into the valve body, then tighten it with the valve socket and pliers.
11. Repeat the previous eight steps to install new seats and stems onto the diverter and cold-water faucet handle.
12. Apply plumber’s putty to the back of each escutcheon plate, then hand-tighten them onto the stems. Remove any excess putty that squeezes out.
13. Screw the handles onto the valve stems.
14. Snap the index covers back onto the handles.
15. Remove the cloth from the drain, turn the water back on, and test your work.