I'd have the surgery done, and quickly. Mainly because of his age and odds of success.
I'd have to absolutely trust my vet as much as I do my family doctor.
I think much like Greg, in that I'd consider it a death sentence, first. I'd have to assess the situation based on information. I wouldn't think of the cancer any differently than if he was run over by a car, or in some other sort of accident. I'm very pragmatic, and don't think at all about what might happen a year down the line because I'm a firm believer that I just have today, and that plays in all my decision making. I'm never slowed down or stifled by "what if's?", so I'd consider my good friend in just that light.
If he's going to be better for the surgery at the end of the day, done deal.
I wouldn't consider the chemo and radiation at this point because it's not even part of the equation, nor are recurring tumors.
Being that it sounds like the surgery would be a success, I'd see if the he wants to go for a ride.
