How do you replace a garbage disposal?

There are two parts to replacing an old garbage disposal unit: First is the unit itself and second is the electrical supply. Replacing a unit is surprisingly easy. If you have one of the main brands from WasteKing or Insinkerator, they have standardised twist and lock fittings - simply twist off the old unit and twist and lock on the new unit under your sink. If you're changing from one brand to another, there are adapters that simply bolt on under your sink. 

For the electrical side, you should turn to a qualified (and certified) electrician. Often, these units simply plug into a wall socket under the sink, in which case it's easy. However, many are hard-wired in to a wall adapter with an RCD short-circuit protector and these need to be fitted by a professional.

Hope this helps!

Garbage disposals are a bit tricky and must be handled by a professional like a handyman. You don't want to get into an accident while doing it.

Consult with and get bids from reputable handymen in your area who have extensive experience in this sorts of stuff like I do when it's time for house fixing.

The husband is not so good with... Well.. His tools.

You can refer this video for replacing the Garbage disposal, this has helped me a lot.