Hope all goes well for the Mrs, Dave.
I've had two operations under General Anaesthetic, and while I can't say either was a particularly good experience (the second especially because they also applied a nerve-block, but failed to actually block the correct nerves! When I woke, I had a screaming agony in my wrist but couldn't move the rest of my arm or hand!), each was in its own right, just fine.
While there is a risk with all operations, it's worth remembering that, like plane flights, the absolute vast majority of a very large number goes on exactly as planned with no problems.
Less time worrying, more time looking for appropriate Get Well Soon cards, flowers, grapes (and chocolate!). :)
Roo