There is not a hole in the glass? I have been looking at mine for months and figured that I would be left with some kind of hole if I removed it. Could someone clarify?
Correct, there is no hole, at least on my 2001 Denali. The interior wire and exterior antenna are inductively coupled (very clever!) so there is no need for a through wire.
Just be careful with the razor so as to not scratch or nick the glass. Slow and steady does it cutting decade old foam tape. A little bit of acetone on a rag removes any remaining glue residue. But do be careful inside the vehicle, fumes can accumulate, and acetone can damage plastics.
It took me about thirty minutes total to remove the exterior antennas (my vehicle had two). I haven't tried to remove the interior antenna cable attachments yet.