Well, first off you're not on 5mg of methadone. You're on 15mg per day and that is absolutely enough to give you w/ds. That said, if you had an easy time getting off vicodin, you'll have a similar experience most likely -- albeit a longer one because meth stays in your system much longer than hydrocodone (the one narcotic of the two active ingredients in Vicodin). It is still a low dose, though, and you should be able to manage it with a physician's help. You might ask for clonidine to ease the w/d symptoms.

For pain, you might try Tramadol -- has narcotic tendencies but less addicitve and somewhat helpful with pain. I assume you have been through the NSAIDs and Cox-2s etc.? For pain, if you can get along with non-addictive anti-inflams (ibuprofen, naprosyn, voltaren, mobic, etc.) you'll ultimately function better. Good luck.