Note how all of the parts of the old unit attach before you remove the garbage disposal system. Disconnect the power by pulling the cord, fuse or switching the disposal circuit breaker to off.
Replace the old garbage disposal using a pipe wrench or tongue-and-groove pliers. Remove the slip fittings on the P-trap, empty the contents of the disposal into a bucket and disconnect or remove clamps, tubes and other fittings that connect the disposal to the drainpipe.
Disconnect the electrical wiring and take out the electrical cover plate screws. Remove wire connectors and use a voltage meter to make certain there is no power.
Hold on to the disposal while you loosen the screws on the side mountings. Turn the locking ring counterclockwise to release the old unit.
Remove the old mounting ring and the sink flange. Take out the screws connecting the ring to the flange (see Resources).
Clean up the area before installing the new unit. Remove old putty, sealing gasket and any other remnants left behind.
Follow the directions on the new unit to replace a garbage disposal. Make sure you unlock the separate pieces on the mounting assembly if necessary.