A good place to find an editor is at the Editorial Freelancer's Association. http://www.the-efa.org/.
Seth Godin (author of a dozen best sellers) wrote this about editors:
"For the last twenty seven years,every single movie that managed to win the Oscar for best picture was also nominated for best editing. Great products, amazing services and stories worth talking about get edited along the way.
"Most of the time, the editing makes them pallid, mediocre and boring. Sometimes, a great editor will push the remarkable stuff. That's his job."