Adding power accessories

As a new member making his first post I think that the moderators and posters here provide a lot of good information here. Hopefully someone here has some experience in this area. I want to convert manual windows, locks and mirrors to power in an E-series cargo van? From online research I have found that there are differences in regulator used for power and manual windows but most doors are pre-drilled for both types. My main question is how much of the existing wiring harness is wired for the windows, locks and mirrors if the doors were swapped with doors from a conversion van? I think it might be easier and less expensive to swap doors rather than modify the existing doors. Has anyone here had any experience in this area?

I just found a thread, "wiring diagram for power windows & locks" in the Econoline forum for a 1991 van. Hopefully it will be the same for newer vans. According to that post the harness was already wired and the connector from the replacement door just plugged right in. I haven't bought the van yet but most of the cargo van I have seen don't have power accessories.