The fourth illustration was found! Huzzah!
I input changes for seven more chapters, plus did some continuity checks. Then I scanned in the illustrations--that went better than expected, which is kind of a relief. The drawings will need a little cleaning up (some among my crack team of illustrators do not erase as carefully as they could), but there aren't a lot of weird digital artifacts or anything.
Pretty soon I will begin the layout--whoo-hoo! I'm going to try using actual layout software this time around (no more Word), presumably renting Adobe's.