10 - 30 minutos
Water damage to phone, so battery discharged twice as fast than before.
Pretty OK aside from detaching the original battery from the glue strips. It's glued *really* hard, unlike in the iPhone 4, so pulling the plastic flap on the left will just ruin it without nudging the battery even a bit.
Really get the Plastic Opening Tools recommended in the guide! I suspect they'll prove really useful.
I forgot about them and had to struggle with a flat screwdriver head and several plastic knives to carefully pry the original battery out, as it was so heavily glued. Luckily, I managed to do it without piercing the battery at all, although it's fair to say, the battery's right edge had a completely different shape when I took it out :)
After removing the original, unpeel most of the glue strips (use nails to slowly unroll from one side, then try to grab with 2 fingers and pull) so that you never have to go through that process again.