The only time I ever replaced a handle was when all that was left of the handle was where it was attached into the head and a four inch long jagged stub. Took forever, even with my grandmother's help to remove all the fencing steeples and tar that held the top of the head on.
As far as putting the head in a vise, I have placed all my axes in my smallish un-padded vise and they haven't been even scratched--probably thanks to the coating of rust, which I've decided not to remove since it isn't that bad.