10 - 30 minuten
I've had my 4s for almost 3 years now, and the battery was a little lack luster to say the least. I would have to conserve the battery by being really choosey with what I did with it because it would die by the end of my work day if I wasn't careful- kind of the opposite purpose of having a smart phone. I always carried a charger around with me because I hated getting stuck with a dead phone. Eventually I just bucked up and bought the replacement parts and tools from ifixit.
The repair went well. There were a couple moments of absolute terror that I had broken everything, but it ended up all right, and turns out- no reason to freak out. The first part was I was SUPER scared I was stripping the pentalobe screws that come factory on the 4s. Turns out the screws are so tiny and my glasses are so $@$*, I couldn't tell the screws were actually turning.
The second little bump in the road came with the ground contact- the little gold bit that has to touch the back of the case. It was pretty loosey goosey- like moved ALL over the place, and I was worried that I had dislodged something that should have stayed put.
I also ended up breaking the exposed clear plastic that supposed to help you get the old battery out, so I had to get in there and really wiggle it out.
All in all took me about 15 minutes, even with the melt downs.
Bonus? Now I feel a lot more confident about doing repairs on other stuff of mine.
Before you start taking everything apart, get acquainted with the guide, and the parts you're going to be moving around. It'll go a lot smoother if you know what you're looking for instead of being like me: "this screw looks right, I'll just undo it. huh... I don't know if this should be flopping around... oh no. Is this the bit that's NOT supposed to come undone?? Oh god. Oh god. I broke it. It's done. Toast. Donezo. &&^&. I can't afford a new phone right now! That's why I did this! &&^&." Figure out what's supposed to move, and what's not. Even with the guide right in front of me, I wished I had studied it a bit more.