I just upgraded mine. Download the torrent (you can find online if you look), buy a 32gb USB drive, search for sierra's email address and email him for an FSC code. He will charge about $65 for a FSC code. You can do it yourself. Never heard of those errors the dealer is talking about.
2013 335i M sport 6MT --Sapphire Black Metallic/Black Dakota, premium package, technology package, dynamic handling, black grilles, 5% tint--