Replacing mirror

I took my car to the paint shop recently and the broke my drivers side mirror motor, well really they broke of the tabs that hold it in place. So i went to the junkyard and got one that didn't have broken tabs i installed and I broke the points were the screws hold it in place when I tried to put the mirror back on. my question is does anyone no how to install the mirror without breaking of the tabs that hold the screws in place. Help would greatly be appreciated.