I've finally decided to give Gnome the boot...
I was hoping that something like "dpkg --purge gnome-session" would warn
me that packages a, b, c, and so on would also be removed because of
dependency issues. It didn't... So, I have to remove things "by hand",
individually. But, something like "dpkg --get-selections | grep gnome"
reports some handy info. I can do something with that, can't I ?? It's
definitely a start too. After that, "deborphan" or similar can help me
clean up after that.