Montana (8 p.m., TNT) is the first TV movie screenplay by author Larry McMurtry, whose novel Lonesome Dove made a memorable miniseries, whose Terms of Endearment became an Oscar-winning movie and whose scripts for Hud and The Last Picture Show are equally famous. Montana is an original work, a contemporary western set in Rosebud County, Mont., about a family of ranchers. Richard Crenna plays Hoyce Guthrie, who refuses to believe that his cowboying days are over; Gena Rowlands plays his wife, Bess, whose passion for the land places her in frequent conflict with her husband. Lea Thompson (Back to the Future) plays their rebellious daughter, Peg, Justin Deas (Santa Barbara) their son, Clyde. The story focuses on the changing face of Montana as a result of land sales to big-money developers. Hoyce prefers to sell and move on; Rowlands prefers to stay and fight. The environmental viewpoint is particularly strong in this film, shot on location in Gallatin County, Mont.