This episode's headline: News Maker; Convention Preview; '88 Campaign Analysis; Pop Star. The guests include OSCAR ARIAS, President, Costa Rica; LEE ATWATER, Bush Campaign Manager; DAVID GERGEN, U.S. News & World Report; MARK SHIELDS, Washington Post; CORRESPONDENTS: CHARLES KRAUSE; JUDY WOODRUFF; JEFFREY KAYE; ESSAYIST: PENNY STALLINGS. Byline: In New York: ROBERT MacNeil; In Washington: JAMES LEHRER