5 - 30 minutos
My iPhone 4 went for a swim, and while I got everything nice and dried out, the battery was completely messed up, causing my device to constantly reboot all day.
Fixing it was incredibly easy. I was a little afraid when I saw the water led to a little rust on the inside screw, but luckily it still managed to come out.
I found it easier to connect the silver connector before fitting the new battery into it's slot.