Steps #4 and #5 went smoothly. Carbon Copy Cloner works like a charm and it allowed me to recondition the hard disk while booting it off the external HD.
We're back up and running. I'm redirecting some caches and scratch disk data away from the newly reconditioned Apple 256GB SSD and into the Drobo for the time being. When the OWC 240GB gets here, I'll point it into the new internal scratch disk.
The wait begins. In the meantime I shall suffer the longer waits from the Drobo doubling as my scratch disk! :)