I do think that this would be a significant win, and will be difficult to achieve. The Cowboys, historically, have not played well in Green Bay.
That doesn't have much to do with this year, but Green Bay is a tough place to play. It will be even tougher considering that the crowd will be amped up as Brett Favre is getting his Hall of Fame ring at halftime of the game.
Dom Capers is an interesting defensive coordinator. He can present a lot of interesting looks (playing 2 DLs, etc.) that can confuse an inexperienced quarterback. He also has some good pieces on defense that can match up with some of the Cowboy weapons - Mike Daniels, Clay Matthews, Nick Perry (he has stepped his game up this year), Ha Ha Clinton Dix and Damarious Randall are all good players. To me, the key for the Cowboys will be if they can block Mike Daniels and Clay Matthews. If they can eliminate both of them, the offense will have success. If not, they will struggle big time.
Defensively, it would be great if Eddie Lacy's ankle either slows him down or renders him unable to play. He's a load and a half. Rodgers has really struggled for 10 or so games, and just appears to be off with his timing and accuracy. Pressure on Rodgers will be key, and also not allowing him to break containment. Pressure in the pocket can really limit his effectiveness.
Prescott has been terrific this year, and I think he will play well. I think that this will be a significant test for him, but the moment won't be too large for him. I can't wait to see it.