Turning Off the Water
Before you start work on this project, turn off your home's water source. There is a valve on the incoming water pipe that leads to the water heater. Rotate this to the closed position by turning it clockwise until it stops turning. This prevents water from running to all your appliances, including the faucet you are repairing.
Removing the Handle and Retaining Nut
The next step is to remove the handle of your faucet by finding a small, round plug at the base of the handle. Take this out and unscrew the screw under it. Moen faucets use an Allen head screw, so an Allen wrench is required. Once removed, the handle pulls off the stem of the cartridge. Next, unscrew the retaining nut with a pair of pliers or large wrench by turning it counterclockwise.
Removing the Cartridge
Once the retaining nut is off the faucet, removing the cartridge is easy. Pull it up and out of the faucet with your hands or a pair of smaller pliers. Grip the body of the cartridge or the space just below the stem to remove it.
Replacing the Cartridge
Once you remove the cartridge, replace it with a new one made for your particular model of Moen faucet. Slide the new cartridge inside the body of the faucet and rebuild it by replacing each one of the parts removed to take the old cartridge out. Now that the stem is replaced, the handle will fit back on the faucet without wobbling. Tighten the set screw to make it secure.