Which ny hospital has the best record for heart stent implenmentation?

No such thing. As a practicing cardiologist in the nyc area, i can answer from personal experience. At each major hospital, there are both extremely talented interventional cardiologists (those who implant stents), as well as plenty who leave much to be desired. You should not look for a specific "heart hospital", but rather a doc who others tell you can be trusted to treat each patient like his own family.
Not sure. I don't live near ny so i can't speak for individual hospitals, but your experience is only as good as the cardiologist performing the stent. I would use the "who would you go to if it was your family" approach if you know people within the medical community.