1) The official link is what you already posted i.e. http://www.barnesandnoble.com/u/Software-Updates-NOOK-Color/379003190/
2) I don't know of any 'message' that goes out. IN forums there isn't a particular thread for updates (that I know of). Usually someone mentions it or starts a new thread.
3) Nook Color is supposed to update automatically when Nook goes to sleep.
you may get a notification in the left bottom corner of the nook when it's updating