Shortly after Nikon announced their revised repair policy for the D600, I logged into their site and printed out the label for my D600 to be shipped back to Nikon for cleaning and replacement of the shutter.
I got the camera body (I didn't enclose anything with it except for a body cap (it seemed like a good idea) and a piece of paper with my contact information (another good idea). It went out on Thursday, February 27th. The UPS tracking showed that it was received at Nikon on the next Monday.
Yesterday, I received a box from Nikon that contained my camera (sorry, no D610) and a statement from them that showed what was done by Nikon. During the entire two weeks they had the camera (including the return time) I did not receive any notification that Nikon had indeed received my camera or how long it would take.