A lot, but not as much as some would have you believe. Sure, a win would put the Cowboys in first place in the NFC East and in the driver's seat for a playoff push in the second half of the season. Not only that, but the Cowboys would have a four game winning streak and confidence in themselves heading into the tougher part of their schedule.
But beating the Eagles Sunday night doesn't guarantee anything except a 6-2 record at the halfway point. Six wins would be great but no team is going to qualify for the playoffs with only six wins. The Cowboys will probably still need at least four more wins in the last eight games even if they do beat the Eagles.
I'm trying not to treat this game as the Superbowl because the bottom line is that even a loss doesn't mean that the season is over. A loss would put the Cowboys at 5-3 which isn't terrible, but it would make a playoff trip difficult because they would probably have to go at least 5-3 over a much tougher second half schedule.
If the Cowboys really are as good as I am starting to believe then they should be able to go to Philadelphia and win. Are the Eagles really that good? Are the Cowboys really that good? This game will help answer both of those questions but things could be totally different by the time the two teams meet again in the season finale. Just ask the Giants...they were 5-0 a few weeks ago and everyone had them in the Superbowl. A few weeks later they are trying to put Humpty Dumpty back together again.
I will definitely enjoy the game if the Cowboys beat the Eagles and shut up their obnoxious fans. But the last few years have taught me that they don't crown the NFL champions in November.