I was snorting 320-480mg of oxycontin a day toward the end. Quit cold turkey with the help of NA. The first few days are brutal. i kept myself busy with NA meetings and other projects. Anything to take my mind off how i felt and the craving. Hot baths helped. Exercise helped. Good nutrition helped. Opiate withdrawal sucks a fat one, but you can get through it.
Once the withdrawal is done what are you gonna do? Do you have a program/support group in mind?