I took my iPhone 5 into the Apple Store because the battery wasn't holding a charge. First the guy tried to tell me the board was fried since I was having problems powering up. (He sees it all the time...) When he was able to power up, he reluctantly agreed I needed a new battery instead of a new phone. After waiting an hour, I was informed that the tech tried to open the phone, but was afraid the glass was about to break, so they ordered a new phone for me instead of replacing the battery. My partner had heard about ifixit, and I decided to give it a try and ordered the kit.
The repair was easy as pie. I was able to open the phone just fine, and the glass didn't break. The battery was easy to replace, and I'm typing this story out on my like-new phone. Apparently I am a lot more able to repair my phone than the tech. And I'm not a techie!!!
If the Apple techs are saying to get a new phone because they "can't" replace the battery, don't buy it! They're just trying to get you to spent a bunch of money on a new phone. Try the ifixit kits first and follow the instructions on their website. It was really an easy repair. Be patient and keep track of the 7 itty bitty screws.