remove door panel... IE like 4 screws, then LIFT UP not out. becareful of the wires attached to the door panel.
then right behind the mirror on the door on the inside there usually is this stuck on noise stuff pull it off. you will see 3 nuts in 3 holes. i beleave its a 8 or 9mm something like that sometimes there smaller... remove those becarefull not to drop the mirror, roll down the window and hold the mirror when you take the last one off.. then unplug the plug... at this point you re-install the mirror you bought..
best thing find one from a junk yard