A methadone junkie literally looks like a walking ghost. Start bringing yourself down quickly. Drop 10 milligrams a day. Get off of methadone as soon as possible, or you may find you're never able to beat it. Many junkies I know will have to be on methadone for the rest of their lives.
Cold turkey is a good way to kick but dangerous for a hard-core junkie.
There is the danger of the shock to your system. Your body is used to living off of the drug, and the abrupt change can actually kill you. The safest thing is to go into rehab or talk to your doctor. But if you have a respectable reputation, this might not be an option. Expensive treatment programs are on the rise.