I just noticed my right side power mirror (just the mirror, not the big
housing) was leaning horizontally being held only by the two wires.  I
can see how it may reattach, but I don't know how to do it.

There's a circular track on the back of the mirror which meshes with a
circular track inside the housing.  On the back of a mirror is a lever
which would seem to permit locking the mirror to the housing once the
tracks are brought together, but this can't be done unless the whole
assembly is taken apart because there's no room for fingers otherwise.

Can I unscrew the four recessed screws to perform this fix, or is there
something I'm missing?

Thanks for the help.
david