Well, I'm not sure what condition your wife is being treated for so my situation may be completely different since I had spinal fusion for scoliosis. But I can still answer questions about the pain afterwards and everything.
I had my fusion surgery about nine months ago and was fused from T5 to L3. I'll be brutally honest when I say that it's no walk in the park, and it's good that you guys are seeking multiple opinions to see if there are any other treatment options available. Because of the severity of the curve in my spine, I really had no other choice. It's a really tough procedure, and even now I will admit that I'm still not free from pain (though I'm not honestly sure if that's normal and am going to see my surgeon this week to make sure everything's okay, because for a while my pain was really mild and has gotten worse all of a sudden). Like I said though, my situation may be different due to the circumstances and also because my fusion is really long.
Pain after surgery, though, is controlled very well so don't worry too much about that. Recovery is veryyy long. Her activities will be restricted for quite a while, and all of the restrictions are usually lifted after a year.
I'm not trying to scare you or dissuade you, because if done by an experienced surgeon spinal fusions are for the most part successful and can help pain improve a lot. The only pain afterwards is obviously from the body healing, and sometimes the hardware causes issues (particularly bothersome if you're very thin). I'm not even a year post-op, so I can't provide lots of info. on what it's like long term after the op, though.
Anyway, good luck with everything!! =]