30 minutes - 2 hours
The old battery just would not allow me to watch more than about an hour of video - a terrible traveling companion.
The repair guide and comments were helpful. Getting the putty knife started was the hard part. Overall the repair worked, but I managed to break the hold button ribbon. Not sure how to not break it since Apple glued it under the battery. So, new battery but a non-functional hold button. Small price to pay for movies on the airplane.
When working the case near the earphone jack the guide says to pry the case and insert the opening tool on the side. This is difficult to impossible since the open side of the case is pushing on the closed side. I found it easier to slide the plastic opening tool around the corner to get at the closed side.