I have to say, even though I am a total idiot with *nix in general, this was easy:
* Go into Synaptic
* Add deb
http://http.us.debian.org/debian unstable main repository and reload.
* Pick "
movabletype-opensource" (and
plugin-core, for good measure)
* That's it!
Feels like it's been a long, long time to get here, but I'm more in the mood to celebrate than complain. Win!