5 - 30 minutos
I broke the little wire/tape deal connecting the battery to the phone attempting to remove it. Soldering/rewiring hopeless. Battery was successfully dismembered in my carelessness.
Smoothly. The (philips) screw driver from the iPhone liberation kit (another worthwhile IFixIt purchase) does not fit the screw on the battery connection terminal but I used some 400 grit sandpaper to do some filing on it so it would be flat enough to use on the terminal but still pointy enough to use on the external case screws. I had to use some micro needle nose pliers to get the screw started but the screw driver finished the task and re-tightened afterwards adequately. I replace the battery and it works great.
Either be prepared for some extra work or shell out for the interior screw driver terminal removal tool on IFixIt. It would be worth while for a tech noob, but if you have the ingenuity access to tool to do it, its not necessary.