Thanks. Yes, I've been following the instructions in post 629; that's what my original quote was to.
Step 2 of that post is now done. For the benefit of any other Mac users as slow-witted as I am, I'll describe what I did in that step.
After confirming the checksum of recovery-clockwork-220.127.116.11-inc.img, I installed the Mac version of Reflash from http://downloads.unrevoked.com/recovery/3.32/Reflash.dmg
. I copied Reflash from the .dmg to a regular directory and ran it from there.
With Reflash running but phone not plugged in, select File -> Custom Recovery , and choose "recovery-clockwork-18.104.22.168-inc" from the place it was saved to. Reflash screen-bottom now says "Recovery image: custom". Only then did I plug in the phone. Reflash found the phone and after asking for my confirmation, began installation and a series of reboots.
After all was finished, I got an error "Error verifying extendedcommand", but on reboot (from a blue, not green, menu on the phone), I was able to go to Settings -> Applications -> Manage Apps , choose "all" pane, -> Superuser Permissions version 2.1; from there I cleared the data, and root checkers confirm that I am rooted.
Many thanks to all!
On to step 3 of post 629 now.