$400+ later and my iMac has returned.
Recovery Disk Assistant employed which then restored my hard drive and recovered my last session on 09-24 from Time Machine. The recovery took 67 minutes (the first 50% took 50 min, the second 50% took only 17 min), but I only had ca 40GB to recover. So far, so good.
The only apparent downside is that backing up after doing all that is taking a honkin' great amount of time.
