Just replace the stock E350 Mirrors to the Ford OEM power tow mirrors. Here's the write up. Hope this helps.
Here are the mirrors from Ebay. Bought them $149 for the pair. Ford Dealer wanted $395 each
Took off the panel behind the mirror. Only one clip.
There are 4 screws, one is located behind door latch panel.
Once the door panel is removed, the mirror's connection is located and clipped on the top left panel. Once unconnected, unbolt the mirrors (4 nuts)
I compared the connectors from both mirrors and I found out that the 2 outside wires were switched. I connected the tow mirrors and played with the controls, and it was totally the opposite direction where I wanted it to go!
I took the mirror out and reversed the wires....ALAS!, it goes where I wanted it to go
Re-connect and re-place everything and start on the other side. PM me if you have any Q's.
Time: Approx 1hr
Tools: Screwdriver (Phillips, small flat head), Socket wrench (11mm, 7mm), Electrical Tape, Wire strippers/ crimper, and wire connectors.