I'm glad you were able to find posts here that helped you get your mind around the Nissen procedure. After my procedure (Feb. 27th), I posted my recovery experience pretty regularly, just for people like you (and me) who are desperate for information and reassurance.
Generally surgeons give a high estimate as to how long a surgery will last. That way when your loved ones are waiting, they won't worry if it goes longer than they expected. I had read that a first time nissen takes about an hour, but my surgeon told me that I'd be in surgery about 3 hours. When I questioned him, he laughed and said that he can't win...whatever amount of time he says, someone finds something wrong with it! I ended up taking about an hour, which I expected.
Yours is a re-do, so I would expect it would take longer. They don't really know what they're getting into until the surgery, so I'm sure they're giving themselves a good long time--enough to do whatever is required. I often wondered what happens with the Nissens done on babies and children. You're the first person that I've talked to who experienced an early surgery.
I don't think you'll find a surgeon who just does Nissens...there aren't enough done to make a practice of just that procedure. As long as you have a doctor who has lots of experience with them--at least 100 (mine had done 300+). My surgeon was a general surgeon, but was recommended by my GI doctor, who said he would not hesitate to have that surgeon do the procedure on him. As it turns out, my surgeon was plenty experienced, and did a great job.
When you say that he isn't specialized in the nissen procedure, do you mean he hasn't got much experience doing them? That would be my number one question. No matter how good he is, his experience with that procedure is critical to the success of your wrap. He doesn't have to do JUST nissens, but he should have done a lot of them.
If you check into this site after your surgery and post questions as new threads, you'll get lots of help from people here. The most unexpected thing I experienced after surgery was the ease of the recovery. I was expecting a horrible experience, and my worries were for nothing. It was a pleasant surprise. I'm three months out, and am eating anything. That's not to say that I don't still have some discomfort with my wrap from time to time (when I overdo it), but nothing that I can't handle.
Please feel free to ask questions...we'll all help you in any way we can.
We'll be there for you, and rooting for a smooth recovery!
Good luck with your surgeon...be sure to write your questions down!
Take care, and don't worry!