Tiebreakers are division record, record against common opponents, conference record, strength of schedule.
GB does have the advantage right now in tiebreakers, if they beat the Bears in week 17. There was an article in GB paper describing them. Its long and detailed but basically today's game against DET is huge for them. They can't lose a second division game otherwise tiebreakers favor Chicago.
Chicago caught a huge break with the Metrodome collapsing. That was going to be a tough game for them next week. If that game is played outside and Favre starts, CHI will win because Favre is horrible in cold weather and takes the home advantage away from Minnesota.
Chicago has caught a lot of breaks this season. No injuries, played Miami with their 3rd string QB, DET with their 3rd string QB (still almost got beat), played PHI without both starting CBs. Makes me think that this is Chicago's year.