It's hard to quantify what a home field advantage means for an NFL team, unless you organize the betting lines on Football games, then you know that it's three points. When the lines are made, each home team is given a three point advantage. So if you see a home NFL team with just a three point advantage, it means that the game is basically a wash talent wise.
For a while the Cowboys were favored to beat the Redskins by five points, which means they were favored in addition to their home field advantage. But now the odds are more even, and the only difference between them to oddsmakers is the home field advantage that Dallas will have. here are the complete odds from SB Nation's Odds Page.
For more on the Redskins vs. Cowboys Monday Night showdown, visit this StoryStream. Visit Hogs Haven for more on the Redskins, and visit Blogging the Boys and SB Nation Dallas for more on the Cowboys.