My blog is mostly back. Various things don't work yet--no OpenID signin (sorry, LJ folks), no list of interesting links at the top right, no extra protection against spam in older entries, no access to months before 2007--but I'll fix those things in the coming days. For now, the basic journal capabilities (read entries, post comments) seem to be working, and I need to go sleep.
What happened: it turns out that dynamically built MT 3.2 is incompatible with PHP 5. So I had to either switch to a statically built blog, which I wasn't willing to do, or upgrade MT. I'm still not ready to upgrade to MT 4 yet, though I'm sure I will eventually; luckily, I had previously downloaded MT 3.3 in anticipation of upgrading to it. I followed Elise Bauer's useful A Safe Way to Upgrade to MT 3.3 instructions (though those instructions are probably not complete enough for anyone who hasn't previously installed and/or upgraded MT) (and I failed to follow her very first instruction, which starts out "Do not attempt to do an upgrade late at night when you are about to go to sleep"--that was a wise idea, but I really didn't want to leave my blog totally broken overnight), and then I checked her 3.3-compatible plugins list. I also found Six Apart's official Changes to the Movable Type Platform for v3.3 page very useful, especially the Typekey authentication section and the "Order of template tag attributes matters" section.
After getting the blog itself up and running, I tried installing the new versions of MT Blogroll and the OpenID plugin, but I couldn't get either one of them to work. I'm way too sleepy now to figure out what's up with those; I'll deal with them over the next couple days.
I should mention that the upgrade process was, overall, pretty painless. Nice work, Six Apart! (Except for the part about not supplying upgrade instructions of your own, that is.)
Must go sleep now.