Should I consider taking methadone if I have been on a pain contract for two years taking 40 mg vicodin daily?

Sure. You might do better with stable Methadone 5 mg 2x-3x a day. This should keep a stable blood level of pain medicine rather than the up and down plasma level of vicodin.
Tylenol (acetaminophen) One of the major problems with long term use of any hydrocodone preparation in the US is that hydrocodone is not available without varying doses of APAP, or Tylenol. Why this is the case is anyones guess. Oxycodone is available plain, as are many other opiod analgesics. My concern with continued Vicodin, anexia, lortab, usage is cumulative liver damage from the acetaminophen.
Methadone for pain. Methadone can be useful for persistent pain but it may be more dangerous than vicodin. 40 mgm hydrocodone is not a very large dose. Methadone can decrease tolerance (the body's need for more pain meds to achieve the same result) and so it must be used carefully when switching from another opioid. It can interfere with the electrical conduction in your heart and produce a fatal arrhythmia.