Brian Lawson wrote:
... My question is: Should I remove that existing corner-bead so I can
get at the actual "edge" of the existing drywall for the mud and new
tape,

I definitely would.

or should I hope to just tape over the existing corner-bead to
the new portion of the wall extension?

I think that this would just create (buried) problems down the road.

I want the extended wall to be "flat" from end-to-end. I suspect that I should remove the beading,

Indeed, that's the best way to get it flat.

but I don't want to damage the ceiling where it joins if I
don't need to.

The ceiling went up first, so the bead should stop a "touch" before it.


If I should rip out the old corner-bead, I should do that before I
frame the extension, because then the beading will be "trapped" and
impossible to get out..

Right. Note that the bead may be fastened up with tabs punched out of
itself with a special tool, or with drywall screws. Nails are possible,
I suppose.

All comments and suggestions welcome, but ASAP please, because SWMBO
says I'm just dinking around here trying to get out of doing it. ...

You have my sympathy.

Bob