I have been on it for 6.5 years. I can tell you from experience the sooner you get out the better. The Meth literally stores in your bones and tissue. You should take a calcium/magnesium supplement along with a multi vitamin. Try to get started on a good high protein diet to help your body adjust and cut back on sugar!! Drink lots of water and hang in there. It's still early enough for you to get out. As I said the sooner you get off the better. Good luck.
I spent many years on and off methadone and can tell you better start getting off. It much harder after a couple or so years go by, believe me.
My understanding, though I've never been on it, is that it's given right away, generally around 30 mg. and you're opiate is removed. The methadone will greatly reduce s/s of w/d but not eliminate them completely. The methadone is highly addictive so it's reduced as soon as possible if not the next day by 1mg intervals or so.