Welcome to the freakin' club. Same thing happened to me.
Luckily my glass part was intact so it only cost me about $120 for the brace (or housing) The silver part is only plastic.
You need to unscrew from inside, I think like 3 small screws around the speaker.
Behind it will be only one bolt. Imagine that?
I had to also take off part of my driver's side door pad, but be carefull not to trap your Lock pin (one of the 4 things that go up and down as you open and close your car...
sorry my English is limited).
I made that mistake and couldn't arm my car, because it was cought.
If your heated glass is broken, make sure you unplug the wires gently (they look like speaker plugs) off the mirror.
It took me about half an hour to complete the whole swap. Like you, at first I was intimidated, really for nothing.
Alright, I took all four screws off the panels. I popped off the holding clips around the edges of the door. Things were going great... How come I couldnt pull the panel off enough to get to the first screw on black plastic that holds the tweeter?
I had the same problem, I think. But I did figure out how to unscrew it somehow. See the truth is I don't remember much it was over a year ago. So sorry if I didn't tell you the right number of screws.
All I remember the after you got the plastic off there is only like 1 big nut hodling the mirror brace.
I have fixed the mirror!!! Thanks to a fellow dubber from Canada (with a Bentley manual) The door controls had to be removed to get access at three huge bolts that hold the entire panel to the door frame. It was cake after that. I don't know if anyone cares but I took pictures the entire process.