So, my ex wanted to use a mediator. Me, him, a mediator, no lawyers. My lawyer advised against it -- because my ex is a master manipulator, and he had repeatedly said to my lawyer that "if I just get her in a room with me, I can convince her to come back to me."
I would only use a mediator if you know for sure that you won't let yourself be emotionally blackmailed into accepting crap you walked into the room determined to not accept. Of me, it would have been a disaster. I spent almost five years paying off my lawyers (mailing the last check today, as a matter of fact), and it was worth every penny.