I had assumed that, since RAID arrays were not uncommon these days, someone else would have come across (and solved!) this problem. However, a Yahoo search of the Web today using words in this thread title came up with only one hit. That involved an American who was happy to experiment with his system and eventually replaced the hard disks. I'm not in that position, and the evidence is that both of my disks are ok.
Even broadening the search to the repair of all RAID arrays only found around six references, mostly involving large RAID5 Unix systems.