15 minuten - 1 uur
My iPhone 5 battery was in pretty bad shape, lasting about half a day and often dying when supposedly at 20%.
Swapped out the battery without too much trouble and my phone is like new again.
I didn't detach the display ribbon, just held the front of the phone up with one hand while switching out the battery with the other. It was a little tricky, but I think a lot less trouble.