It's easy to replace.
Open the door and remove the rubber boot on the same side the door switch is located.
If you look close at the rubber boot you will see it's held in place with a metal band and spring.
Just pop the band off and peel back the rubber boot just far enough next to the door switch for you to get in there and replace the switch.
The switch is help in place with three screws from the front.
Maybe Mr. Fix-It has something to add, but that is how I replace them.