My husband's iPhone 5s's battery has been really bad for the past year. His battery alone would not last him the entire day despite the fact that he barely touches it during work. When he gets home, his battery would be on the verge of dying so he constantly sits by a charger all day.
I had mistakenly ordered the battery for an iPhone 5 instead of the 5s. iFixit was very generous in their return policy and accepted the iPhone 5 battery repair kit back. I reordered the 5s battery repair kit and finished off the phone. Even with this mistake, everything went smoothly. The directions were easy and pretty clear.
1. Take your time. Everything inside the phone is extremely fragile.
2. Keep tape (sticky side up) to hold all the very tiny screws.
3. Anything that you took out, keep them in that particular order (you might not be aware that one screw may not be good for another slot).
4. DO NOT PUSH ANYTHING DOWN! Simply and gently tap flaps in place.
5. If you're not sure anymore, CALL iFixit. They are very helpful and they know what they're talking about.