drivers side mirror 93 4 runner sr5

hit a pigeon today and my drivers side mirror glass exploded theres a white disc with a spring in the middle in the center of the motor does this need to come off?and does the backing for the glass go on the inside of it so it pops into the fingers ?how do i get the disc off? i ordered a glass from local dealer do u know if the little arms on the back come with it cause 2 of the fingers on one of the arms broke also, just curious because i really dont know if theres anything missing or not and curious what i need to do to reinstall the mirror ? thanks for any help