I’ve experienced the multi-hour OS upgrade in the past. It turned out to be because of having TexLive installed. Does Tonya use that? My best recollection is that what happens is the upgrade process moves and restores all the files in the folder where TexLive installs its many thousands of tiny files (maybe /usr/local). It takes forever. I also remember there was a control key I could press to see a status window showing what the upgrade was doing (which was how I identified the TexLive files as the issue). Maybe Ctrl+L or Ctrl+T. I know Ctrl+T works to get status when using dd to copy disk images.
Edit: Looks like it’s Ctrl+L