Moral of the story: don’t do anything when you’re tired as hell.

So, the dilemma below is actually solved pretty easily with the following.

1. Download Gallery2 version 2.02
2. Download module: PublishXP from that SAME VERSION.
(where I previously downloaded PublishXP from ver 2.1!!)
3. Delete Gallery2
4. Upload Gallery2
5. Install modules: PublishXP, imageblock, imageframe
6. Delete plugin: WPG2 and re-install, and re-configure.