vh- sorry to hear of your predicament.
Its a little difficult to give specific advice about your wife's condition, without knowing the full facts of her case.
I guess if I was in you situation I'd be asking some basic questions of your surgeon/cancer team.
have you performed this surgery before?
what is your success rate?
how often do things go wrong?
how can you support your wife to make sure she is as fit as possible prior to surgery?
What are the alternatives to surgery?
In the UK we have specialist nurses, who are pretty good at co-ordinating the care of cancer patients, and sometimes are able to approach the experts with the questions you may feel you can't ask. They are called MacMillan nurses. I'm not sure if you have an equivalent in your neck of the woods, but in my experience, they can be very supportive in what must be a difficult time.
Sorry I can't be more specific, best of luck.