if by chance it is a stock windshield---all you have to do is loosen the external scwes and pull it out. there is a rubber gasket that goes between the outter cover and the windshield--it may stick to your windshield. the windshield has slotted monting holes , the rubber gasket doesnt. so be carefull of it. ---yes you do need it.
:waving:It is best to remove the speakers since the nuts are not captive and will generally fall into the speakers when you try to install the mirror screws. Remove both turn signals, disconnect the speakers, (they are quick disconnect type connectors) and the way the connectors are installed on the speaker wires they can't be crossed. Then remove 4 wing nuts on each speaker and remove speakers. Hope this helps!