Mel - you've gotten some great advice and done some great thinking about your plan! Please be sure that if you lay out a boundry, stick to it! I hope that all goes well and that your boundries 'wake up' the wonderful wife and mother that sleeps inside the alcoholic who has taken over her body. Be strong...for all three of you!
Also, I am not sure if you have cable or DirectTV or something, but there is a show called 'Intervention' that you can watch that may give you a general idea how a professional intervention works. Sort of a reality show that follows the people planning it, the user thinks they are filming a show on addiction, and then they 'spring' the intervention on the user. It's on AMC, I think...anyone can chime in if they know. Thanks!!