cylinder misfire

just recently purchase a 2000 BMW 323i/75kmiles. I notice that the car hesitates when in acceleration. So I took it to my mechanic to have it checked out. He discovered 3 problems. Cylinder 3 is misfiring; fuel and air metering; and a leak in the transmission. I still have a warranty with the dealer where I bought the car. Am I better off getting it serviced in an authorized BMW service center? Or, just take it back to the dealer.
I want my car to be in tip top condition. Do you guys have any recommendations as to how should I decide on this? Thanks!

First of all, why the HELL did you make this thread in the Bugatti forum? I think it would do a little better in, oh, I dont know, the BMW 3 Series forum. But apart form that, a cylinder misfire is caused by the timing of the spark plug on that individual cylinder. I would say change the spark plug with a new one, such as a Bosche Platnum, Platnum 2, or Platnum 4. They all make great sparks. You could even buy 6 and not have a problem. Or you go to the dealership nad they'd replace it for free. So whatever you want to do is fine. Next time, however, post all BMW questions in the BMW forum.