Quarterback Joe Theismann of the Washington Redskins has been hired by ABC to work as a commentator on the Super Bowl telecast Jan. 20, the network announced Monday. Theismann will work with Frank Gifford, the play-by-play announcer, and Don Meredith, the other commentator. It had been reported earlier that both Meredith and O.J. Simpson, the regular "Monday Night Football" commentators, would not be in the booth during the telecast, but ABC apparently changed its thinking about Meredith's role. Sources had said that either San Francisco Coach Bill Walsh or Miami Coach Don Shula might be used, but neither is available, since their teams will be playing the Super Bowl game. The network also announced that Coach Tom Landry of the Dallas Cowboys will serve as expert commentator on the pregame, halftime and postgame shows with Simpson. Also working those shows will be Al Michaels and Jim Lampley.