The Genius's at the Apple store told me I needed to throw away my phone and spend $700 for a new one. I am too cheap for a family plan and use a $10/month GoPhone plan from AT&T. $700 is too much for the amount of use I get out of this thing.
I am 63 years old. I cannot afford to throw stuff away just because the battery is tired. My hands shake a little and my eyesight is not as good as it once was. It took me about 45 minutes to take it a part. Getting the battery adhesive loose was the worst part. I tried the hair dryer trick and worked it from all sides with the spudger and it eventually popped loose. I didn't realize at first the adhesive on the new battery is covered with a piece of tape. Eventually, I found a loose corner and was able to peal the tape off the new battery. Push the battery down good and hard to make it stick into place.
By then I realized I could not see well enough to reassemble all of those little screws. I went to Office Depot and bought a free standing magnifying glass. I had also taken care to arrange the screws into four little cups like you put ketchup in at McDonalds for reassembly. A pill box would probably work, too. Still the reassembly did not go smoothly. I could not get the holes on the logic board to align and accept the screws. After about an hour I concluded I needed to unscrew the camera. I snapped the camera into place but did not attach the screw until last. I removed the screw from under the DO NOT REMOVE tag, also. This allowed me to align the screw holes on the logic board by starting with the middle screws on either side and working outward. That went well. The camera screw still proved difficult. I used the paper clip to align the clip over the screw hole and was finally able to position the screw into the top. My big fingers do not help. After plugging it into the charger I had only a white screen. I reset to the factory settings using iTunes and it works perfectly.