You can't change anyone but yourself.
As someone who cheated and then moved to polyamory-yes it can be done. However, it requires that the cheater wants to change enough that they are willing to do the hardcore, deep emotional work that is required.
It certainly CAN be done (changing) but it's not easy to look at yourself and find all the shitty parts that need improved on. That's what ya gotta do to change any negative aspect of yourself. And, if it doesn't come from within YOUR OWN DESIRE-you'll end up failing most of the time-because you won't have the fortitude to carry on.
"Love As Thou Wilt"