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yes you will need to remove the quarter glass to get the main one out. It is not that difficult
Did you look on the manual page in the Tech section? http://forum.73-87chevytrucks.com/smforum/index.php?topic=30115.0Specifically: http://www.73-87chevytrucks.com/techinfo/7387CKMans//Service/X8432_1984_GMC_Light_Duty_Trucks_Service_Manual.pdf#page=1679