Does anyone know anything about Amazon's print on demand?

http://www.kboards.com/index.php?topic=139442.0

The service is Createspace.com. There is an existing conversation about the service at the link above that will probably answer all of your questions.

Yes, overediting is possible.  Overediting is also bad editing.  And anyone can overedit:  the author as well as an editor. 

A writer should step back from any draft for a week or so, then view the work with fresh eyes.

A good editor will always aim to preserve the author's voice while making suggestions to reduce wordiness, to improve the story's pace, and so forth.

An author--especially a self-published one--has the final word on the story.  Only accept or make changes that improve or advance the writing/story.

Thanks, Julie! I will check it out.

Yes createspace is very good. Good support too. While ebooks will likely make up the greater portion of your sales, some people do prefer paperback and they handle that well.