Paul McCartney is giving marriage another chance. He's now engaged to his longtime girlfriend, New York businesswoman Nancy Shevell, sources tell People. It's marriage No. 3 for the former Beatle, and the engagement comes about three years after his uber-nasty divorce from Heather Mills. McCartney's fashion designer daughter, Stella, is said to be "thrilled." McCartney is 68 and Shevell 51. Click for more on the engagement.