Oh, it's a big operation, he's got every right to be worried - on the other hand, it's also a very successful procedure. I was in hospital with loads of 'knees' and all were a huge relief to their new owners.

I'ts easy to say don't worry, it'll be easier than you think, but the truth is, it is!!!!!!! Something you can't know until it's all done.
Wishing him a speedy recovery.
Donna X