Here is the drama behind the creation of Manhattan, a first-of-its-kind prime-time television series produced by Melvin Wechsler. Tempered by tragedy, seasoned by success, a man with a Midas touch, Mel Wechsler will assemble a dazzling cast: Sabina Quarles at forty-five has managed to maintain- by dint of spunk and surgery- the body of an eighteen-year-old. Jane Adams is an earthy thirty-nine-year-old beauty. Jack Taylor, the leading man, is a paragon of professionalism. Gabrielle Thornton-Smith, charming ingenue seems to have appreared out of the blue. And Bill Warwick, plucked form the ranks of struggling young actors, is now slated to be the nation's new hearthrob.