at the very bottom of the door is a mount that holds the vent window frame down. there should be a plug in the bottom of the door remove this plug and you can access the nut. after you remove the nut you can lift the frame out, as you bring it out rotate it back and the frame will clear the front area in the gap. also there is a allen screw that holds the vent frame. just below the vent window there is another plug a small one in the door, if you only loosen the screw and not take it out the nut will stay in place. a good idea is to only take apart one door at a time. once the vent frame is out you can see how to take it apart to change the glass. reinstall in reverse procedure