You have to drill out the rivets that attach the 1/4 vent frame to the door glass channel.
Once you have done that remove the nut and spring from the botton pivot of the vent window
Then you hold the vent window and pull the outer section at the top where the rubber sits away from the top pivot till it if no longer held in place by the top pivot.
Then its just a matter of sliding the botton threaded pivot out to release the 1/4 vent frame and glass.
Will post more pictures when photobucket will let me