A Simple Guide to Garbage Disposal Replacement Garbage disposal replacement is usually a manageable DIY project when you are swapping an existing unit, the under-sink outlet or wiring is already in place, and the new disposal fits your sink setup. Most same-mount replacements take about 1 to 2 hours, and doing the work yourself can save roughly $80 to $200 compared with hiring a plumber. Before you start, make sure the old unit truly needs replacement. A reset button or simpl