I've done this on a 2000 E250 although the chassis doesn't matter pre se--body parts such as glass are all the same for any one year, back to 1992 for the most part.
I used factory parts which were simply transferred from on E250 to the existing E250. The power regulators, power door lock solenoids, the complete door wiring harness and the actual door panels too.
Along with the door wiring harness I clipped the mating halves inside the cabin to make adding this feature to a chassis not originally factory equipped van. It was a bit of a challenge so depending on the year you're working on, the level of your vehicular wiring experience and tool selection it will be "easy" or "difficult" based on those elements.
If you choose the eBay stuff I have no experience with such parts. FWIW I'm in the auto/truck glass biz and tend to never use anything aftermarket if possible. I'll pay extra for long-life parts.