Well, you can tell if you have the correct cross car harness for the locks and windows by looking up under your passenger footwell, to the right of the chime box, and seeing if there is a silver power lock relay right there or at least 2 or 3 connectors (can't remember if there are 2 or 3) for one to plug into. Or you could pull up your shift surround and look for the power window switch connectors under your blank black panel.
If you are going to have to get the cross car harness for the windows and locks, make sure you get one that came from a car with the third brake light. There are two connectors in the area behind the IP that changed when the third brake light was added.
I completely removed the dash when I swapped in power locks and mirrors, made it very easy. The mirrors are on a completely different harness, by the way.