But of course I would be thinking long and hard about NOT changing the skin but repairing yours. Door skins are tough for many professional bodymen, for a first timer it can be a disaster. And this is with quality OEM skins, if we are talking about your typical aftermarket made in China junk, it can be maddening for anyone!
It may be the best choice, but look at it long and hard first. What is the reason you want to change the skin?
If you do decide to go with the skin, here is a little tutorial to door skins. "Basics of Basics" Door skins