Turn off the main water supply to you home.
Unscrew the three-handled shower plate from your shower. Use the screwdriver to unscrew the plate. Pry the faces off the handles and loosen the screws beneath them. Remove the handles from the shower. You’ll be left with a hole in your shower wall with pipes behind it.
Unscrew the old shower valve from the pipes with the wrench. Remove the diverter from the pipes.
Cut through the hot and cold pipes, the pipes on either side of the middle pipe, with the hacksaw. The pipes need to be cut back by 2 to 3 inches behind the wall. Wrap two to three layers of duct tape around the surface of the cut pipes.
Place the washers on the inside of the shower valve. Place the shower valve onto the middle pipe and tighten the nut on the back of it. Slide the pipe extensions onto the cut pipe ends and tighten them together with the nuts and wrench.
Insert the hot and cold pipe extensions into the valve and tighten the nuts.
Slide the new faceplate over the shower wall and screw it in place with the screwdriver. Slip the new handle over the valve and tighten the screw over it to hold it in place.