In its mano-a-mano battle with NBC's morning leader, the Today show, Good Morning America has scored a major "get," landing an interview with with Quintana Shotts, an ex-wife of John Mark Karr, the man who confessed last week to killing JonBenet Ramsey. Shotts married Karr in 1984 when she was 13 and he was 19 but filed for an annulment nine months later, saying in her complaint that she was "fearful for her life and safety." The interview was scheduled to air today (Wednesday). Meanwhile, it was announced Tuesday that Sam Champion, the dapper weatherman for WABC-TV, ABC's owned station in New York, will become the "weather anchor" and "weather editor" for GMA beginning Sept. 5, the same day that Chris Cuomo is due to make his debut on the morning show as its news anchor.