I don't remember all the details, but you take off the window frame, then take off the access cover at the lower part of the door, and also one in the middle, if I remember correctly. The inside door handles may have to come off, too. They are held on with 'C' clips, and maybe a set screw. The vent window frame needs to be removed; I think there is a bolt at the bottom of the frame, and screws at the top. When it is loose, run the door glass all the way down, then tip it toward the back of the door, then you can work it out of the door. When the vent window is out of the way, run glass up enough to get ahold of it, then you can slide the glass and the retainer toward the front of the door and out of the regulator mechanism. The retainer that runs in the regulator comes out with the glass and is used on the new glass, but there is a felt or heavy paper cushion that wraps around the glass to cushion it in the retainer channel.
The channel in the door frame is held in with screws, if you need to replace that channel- you probably should replace that. The same goes for the vent window channel- for the door glass.
After reading all this, I'm sure I left something out, or said something that is incorrect, so maybe someone else will help out. If not, I'll see if I can find better instructions. The last time I replaced one of those windows was sometime in the last century...
Harvester