What usually happens is the Packers do one or two stupid things or the Lions get one or two lucky breaks to start the game, then the crowd gets into it (even with all the Packer fans, that place can get loud), and the Lions feed off that energy. I think this is a very different Detroit team from the last few years and, while they're still capable of getting some lucky breaks, they're just not talented enough to outplay the Packers if they do get those breaks, and I don't think just changing the coach will cure what ails them. And with no crowd, they won't have anyone to whip them into a frenzy and play over their heads.
That being said, I agree that the Packers can't afford to come out flat for this one. They can't keep playing the "fall in an early deficit and turn it on to win in the end" game with Detroit. I'd be disgusted, but not shocked, with a loss.