15 minuten - 1 uur
2 years of everyday use on long commutes eventually drained the battery leaving a quarter of a days use on a full charge. Expensive to get it replaced professionally, cheap to do it yourself with the IFIXIT kit.
Sloooowly. Dont rush. Take your time. Took me 40 mins.
Have some tweezers handy as some screws don't magnetically attach to the screwdriver. Lift up display really slowly and once you get the plastic thing in twist it slowly to open up the display further. Don't unplug the cables attached to the display. Prop it up with something so it sits up around 80 degrees. You can still replace the battery without detaching the display. Lift up the LEFT side of the battery using the metal side of the phone as leverage (SLOWLY). You dont want to poke around the right side where all the components are. Once you have replaced the battery, give the battery a gentle firm push down along the top surface so the adhesive will stick to it again (hopefully). I mention this because mine seems to have gone slightly loose now and I can feel it moving if i shake the phone. Gonna open it again and try it.
Now I have a phone that feels like new again! One WHOLE day of use on a full charge!
Good luck! (Slowly!)