15 - 30 minutos
Almost simultaneously the home button stopped working on my phone and I pressed the power/lock button and it depressed all the way and never came back up - it wasn't pushed down (the 'Swipe to shut down' message never came up), it had just fallen a bit.
This wouldn't have been a huge problem (I jailbreak so I can lock my phone with SBSettings and assigned the home button to one of the volume buttons), but it's a tethered jailbreak, so I need both the power button and home button to turn the phone on...
I replaced both parts successfully, however it turns out it wasn't the lock/power button that had broken but some part underneath it, and so my phone was permanently powered down :(
If you can get tweezers with a rubber'ish tip, get those. Two or three screws flew out of the grasp of my tweezers as I was removing/inserting them and I spent almost as much time looking for them as I did replacing the parts