After lots of poking around and a few false starts, I finally remembered that my root partition is hda5, not hda1. Once I got that set up, it worked like a charm. Renamed my old modules back into place, put my old kernel back, re-ran lilo, rebooted.
So...I'll be using lilo's boot-menu mode from now on, and I've printed out a copy of df(1)'s output for future reference. Whee.
Now, to see if I can get a basic configuration working...