This episode's headline: Mortgage Foreclosures. The guests include DAVID GREENBERG, Consumer Federation of America; In Los Angeles (Facilities: KCET-TV): DAVID SHULMAN, Housing Economist; RICHARD LOUGHLIN, President, Century 21. Byline: In New York: ROBERT MacNEIL, Executive Editor; In Washington: JIM LEHRER, Associate Editor; KENNETH WITTY, Producer; JOE QUINLAN, Reporter