The ringleader of an international cocaine trafficking ring that included two scions of a prominent Sonoma County family pleaded guilty in federal court to a cocaine-dealing conspiracy. Richard Wallstrum, 45, of Santa Rosa, pleaded guilty to operating a continuing criminal enterprise, distribution of cocaine and lying on a tax return, according to Assistant U.S. Atty. Matthew Pavone. Wallstrum faces a minimum of 10 years in prison and a maximum term of life without parole and $375,000 in fines. He was one of 11 people charged in December, 1987, with running a cocaine operation between California and South America from 1974 to 1984. The ring is believed to have smuggled 660 pounds of cocaine worth an estimated $33 million during the decade it operated, according to U.S. Atty. Joseph Russoniello.