AT THE MOVIES, Sigourney Weaver (left) heads into the jungle as naturalist Dian Fossey in Gorillas in the Mist. Weaver would get an Oscar nomination for the part. IN MUSIC, Bobby McFerrin’s ”Don’t Worry, Be Happy” outduels Guns N’ Roses’ ”Sweet Child o’ Mine” for top honors on the Billboard singles chart. IN BOOKSTORES, Tom Clancy’s latest Jack Ryan thriller, The Cardinal of the Kremlin, is No. 1 on the New York Times fiction list. AND IN THE NEWS, NASA prepares for the launch of space shuttle Discovery, the first mission to blast off since the Challenger disaster 32 months earlier.