Okay, the oem encosures? The enclosure is the door. You take the old speakers out, then you have an oval frame left. Put the new speakers in there and holding it in place, mark the holes. Now drill the holes a bit smaller than your mounting screws and screw the bastard in.
As for the water. the window seals on Contours are crappy, but you should be alright. Just check for rust while you're in there.
