Check on you-tube for some vids. They'll give you an idea of the process.
I used a jig saw and it was a quick and easy. You can use a sawzall, but I found the jigsaw easier to control. A small cut-off wheel will also work, and makes cleaning up the flare support in front easy. I used a large flat file to finish the edges and then topped them off with door edge trim molding.
I removed the rear fender liners and discarded them and just trimmed the front liner.