My Ipad Retina had a battery that would last only 2 hours. I was not sure if this was standard so I did nothing for the warranty period. On about the 14th month I tried to get it repaired under warranty, only to be told it was going to cost me $370. That's a smidgen under new price. So I decided to try and replace the battery myself.
Not good I smashed the screen. I did get the battery installed OK. I'm in the process of ordering a new screen
Take your time on the screen. No matter what be patient. Use the guitar picks like the instructions say. I didn't because I didn't have any and I now have a smashed screen to show for it.
iPad 3/4 Battery
iPad 3/4 Adhesive Strips
Phillips #0 Screwdriver