You can actually re-use the manual crank door panels--the switches go in the same location as the crank, and all you have to do is cut the round hole into a square hole for the window switch.
If you are going to have the car completely apart, definitely put in the PW. But it has to come apart to do it right--crossover harness is mounted to the back side of the firewall up high under the dash, so everything has to be out of the dash to put it in correctly. The holes for the wire boots between the doors and door jambs have to be drilled with the doors off of the car. The holes in the door jab are two sizes (two layers of metal to go through) and the larger one is to the outside, so it has to be drilled from the outside with the door off. Take lots of pictures of the wire and screw locations when you take it all out of the Skylark because you will need it when you go to install it all in the GS!
Make sure you take all the motors apart and clean/lubricate them well before putting them in the car--it is a major job to get one back out later if it has a problem. (requires removing the glass, and on the doors, requires removal of the vent window).
