Hi Steve,
In my limited experience, most Oncs seem to encourage their patients to get second opinions-- I think that they know that it can bring the patient tremendous peace of mind, and most seem to welcome a fresh take on a patient's situation.
If you'd like to visit Sloan for a second opinion, there is a place called Miracle House which provides housing for patients (all types) that are visiting NYC for second opinions and treatment. You can learn more at
http://miraclehouse.org/ I've never been there, but the rooms look nice-- Oprah had some of them redone for her show.
The other thing to consider re: a second opinion is that a big cancer center will likely have trials that aren't otherwise open to your wife. Even if they aren't appropriate at this time, you at least have started a dialogue and will always have the ability to touch base and see what fits as your circumstances change, or as new drugs become available.
I was treated at Sloan, and I did get a second opinion while I was in active treatment. It brought me a lot of peace of mind.
Good luck with everything.
Jen