Turn off the water supply at the main shutoff valve near the water meter.
Remove the handle which actuates the diverter valve by first withdrawing the single screw located in the center of the handle with a Phillips screwdriver, then by pulling the handle away from the diverter valve.
Pry the chrome escutcheon plate off of the shower's wall with the blade of a flathead screwdriver.
Remove the bonnet nut from the diverter valve. The bonnet nut is what holds the valve's stem within the stem assembly, and can be removed with a wrench.
Attach an appropriate sized deep-socket to a socket wrench, then slide the socket over the diverter valve. Use the socket wrench to turn the diverter valve's stem assembly in a counterclockwise direction until the valve is free. Pull the diverter valve out of the wall to complete the removal.