I think the easiest replacement would be with Insinkerator.
Pick up some plumbers putty while you are at it.
You will have to wire nut the new disposer. There is a panel on the underside of the unit.
They come with pretty good instructions
If you have a dishwasher and it connects to the disposer near the top, there is a plug that will need knocking out. Otherwise, no, you leave that.