When my sister experienced hers...she had to go in for a D&C and she was told around 2-3 wks to heal, but her body was still experiencing issues for 2 months before she finally started getting back to a normal state. I think it varies from person to person, but the average should be 2-3 weeks.
My doc told me it could take a week or longer & I wouldn't know for sure how much time it would take. Suggested D&C, & I took him up on it--I wanted to know it was all taken care of, so I wasn't dealing w/ that on top of losing the baby. (Of course, I had bleeding for a while, but at least I knew the miscarriage part was over.)