This episode's headline: Tobacco Hearings. The guests include JAMES SWOMLEY, American Lung Association; Rep. THOMAS PETRI, Republican, Wisconsin; Rep. LARRY HOPKINS, Republican, Kentucky. Byline: In New York: ROBERT MacNEIL, Executive Editor; In Washington: JIM LEHRER, Associate Editor; JOE QUINLAN, Producer; MARIE MacLEAN, Reporter; LESLIE WEISBERG, Researcher; Videotape Segment: MARK BENJAMIN, Camera-Director; ALVIN KRINSKY, Sound Recordist; DAVID ROTH, Production Assistant