Number of surgeries?
I don't know for sure if the any of the medical associations provide such info, although you could check with the AMA to see if he has been reported as having had problems. I suggest that you look at what people on OH who have used the particular surgeon says about him. That will tell you a lot about him.
First, just so you are aware, the surgeons pages that they keep on here, they can remove negative comments if they want (I didn't know that until recently). If you can actually get a conversation going with an actual patient, that would be better. In person supports groups are tricky, the people are nice, but the culture tends towards the group and the members becoming one big infomercial for the surgeon, people who have problems/complications are usually not going to attend support group. I'm not sure what surgery you are planning on having, but in addition to the usual questions, I would specifically ask what does this surgeon know about the digestive system and function? Are they able to recognize, and how, if their patient is having gastric emptying issues that last beyond normal healing periods? If that happened, how would they diagnose and treat the problem? How will the surgeon isolate your Vagus nerve and prevent damage/dissection of it during surgery? These are just a few ideas. They will give you their "stats" on death/leaks/blood loss/infection, but the other questions are the gray areas that most (not all) don't talk about. I hope this helps to open a dialogue between you and any potential surgeons.