Have fun getting it back on. there must be some trick to it.
the way we did it, had my wife hold the mirror with one of the pins in the slot. then placed one of my rubber dead blow hammer handles against the mirror base on the oposite side. used a 3# dead blow and whacked on the head of the first hammer. took about 3 tries and it popped in.
only broke 3 of my wifes fingers

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Charlie