Promoter Bill Graham has been posthumously named the 20th winner of the American Music Awards’ Award of Merit, granted in recognition of “outstanding contributions over a long period of time to the musical entertainment of the American public.”Graham’s son David will accept the award during the show’s ABC-TV broadcast Jan. 25. Tribute will be paid to Graham by Dan Aykroyd, John Fogerty, Jerry Garcia, Huey Lewis, Carlos Santana and Grace Slick. Luther Vandross will headline the Scholarship Foundation Dinner and Shari Lewis will present the 1992 Advertising Awards at the 35th annual National Assn. of Recording Merchandisers convention, set for Orlando, Fla., March 6-9. The Vandross dinner is March 7, with the advertising awards scheduled for March 9.