So spent some more time on this and still not getting anywhere. I have a Crucial 500GB MX200 SSD installed (replacement for the failed original drive). I updated the firmware to the latest (MU04) and tried to install 10.13.3 from the AppStore (failed), download (failed) and download of the cumulative combo update from 10.13 (failed).
Interestingly, my SSD, even with High Sierra 10.13.2, is running journaled HFS+ as the file system. I *thought* all SSDs were supposed to be updated to APFS with High Sierra. Mine did not, and I'm wondering if that's the problem now. It does not appear that there is a way to update the drive to APFS.
So - big questions...1) if I wipe the drive and reinstall with APFS - will I get APFS or will I "brick" the drive?; 2) if I'm successful getting APFS and MacOS onto the SSD, can I then recover from a TimeCapsule backup and restore the data, even though the backup would have been of an HFS+ filesystem?