The Cowboys announced their signing of Terrell Owens on Saturday, marrying one of the National Football League's most glamorous franchises with one of its most controversial players. Owens' three-year contract is potentially worth $25 million. The signing of Owens sets up what could be a compelling study in outsize personalities: Coach Bill Parcells and Owens, who alienated two previous employers, the San Francisco 49ers and the Philadelphia Eagles. "I'm a star among stars now," a smiling Owens said at a news conference at the Cowboys' headquarters in Irving, Tex. Owens, 32, called the troubles he has had with previous teams "life-learning experiences."