Dave, I wish you a speedy recovery! If the lambda sensor upstream of the catalytic converter shows an error, then, in my humble layman's opinion, this does not necessarily mean that there is something wrong with the catalytic converter itself. If the sensor upstream of the catalytic converter is OK but the sensor downstream of the catalytic converter reports an error, then I would assume that there is a fault in the catalytic converter itself.
Two years ago, we had the lambda sensor upstream of the catalytic converter break while on holiday in Italy. You could see that very clearly in the OBD2 reader. No more voltage jump. The engine went into a kind of emergency run, which is ok for a short time but produces a very rich mixture. This can mean that your catalytic converter is still ok but that it is coked up. That's how it was with us. After we fitted a new lambda sensor upstream of the catalytic converter and drove a few kilometres, everything was ok again.
