I had this same problem and they also replaced my cylinder head. They told me it was around 14k of parts and labor that was covered. I ended up getting an extended warranty so that I am covered up to 100k as well.
2011 335d M-Sport, Black Sapphire Metallic/Saddle Brown, Premium, Nav
Retired: 2010 335d, Monaco Blue with Oyster/Black, Sport, Premium, Nav, Comfort Access