BOSTON — An 80-year-old man who pleaded guilty to running a massive marijuana-dealing operation faces sentencing in federal court.Marshall Dion pleaded guilty in October. He faces up to seven years in prison under a plea agreement with prosecutors who say Dion has been selling marijuana for decades.Dion in 1985 crashed a single-engine plane in Kenosha County, Wisconsin, and then crawled along a field with two broken ankles as cash floated in the air.