My wife's iPhone didn't keep a charge longer than an hour.
Removing the battery was the most difficult task. Otherwise, the repair went pretty smoothly. The battery connector cable was fairly unwieldy so seating the connector was more difficult than with other iPhones.
Skip trying to pull the adhesive strips out using the tabs. Too flimsy to make that removal work. Go straight for the E-string guitar string method. Getting the string started at the top of the battery is a bit of a challenge but if you can get it under one corner of the battery and then behind the top edge of the battery it is doable. Take it slow and use a side to side sawing motion until you get to the last inch or so. The battery should just pry out easily. When installing the new battery give yourself a little extra room on the connector side. The cable to the connector is not very flexible and extra room is needed to properly seat the battery connector.