The Bears did beat the 49ers week 1 so they do have some ability. Their defense is no pushover, but the Cowboys have played better defenses - and better offenses.
What worries me if the Bears have the kind of offense that will give the Cowboys trouble, a big strong run blocking OL, two good RBs and a QB who can take it to the house on any down by keeping the ball. Their offense sounds like the Eagles, except the Eagles have 3 really good WRs.
But if we go back to the Eagles game, even though the Eagles set up two drives with the run, ultimately the big plays were passes. The Cowboys have to force some 3rd down and make the Bears throw the ball. They also need to sustain their own drives and score points.