7PM This episode's headline: Iran-contra Hearings; Upstairs-Downstairs. The guests include In Washington: Rep. JACK BROOKS, (D) Texas; Rep. RICHARD CHENEY, (R) Wyoming; NORMAN ORNSTEIN, American Enterprise Institute; REPORTS FROM NEWSHOUR CORRESPONDENTS: PAUL SOLMAN. Byline: In New York: ROBERT MacNEIL, Executive Editor; In Washington: JUDY WOODRUFF, Chief Washington Correspondent