Van to Camper Conversion Questions-windows

[Cyn]

Hi All!  I have a 2003 Ford E-350 that I'm slowly converting to a camper.  Most things are fine for me to manage, but I want to add a window to the driver side in the back, just behind the driver seat area.  There are molded in places whre it looks like one could be added in, but I'm really needing to do this on the very-cheap, and have a retired Real-Lite Truck camper that I'd like to cannibalize for whatever I can.  It had a nice clear glass slider window in the back over the dinette that might fit where I can use it, and many small, dark-tinted bubble-type windows in various shapes and some sliders, some stable.  I want the window for light and air for cooling and cooking vent.

Any suggestions or ideas?  Of course, ideally I'd like a nice pop-out Ford van window, but that's not affordable anytime in the near future.  I already have a 14" roof vent with a fan to put in later, do I need a window too?