15 - 30 minutos
My iPhone4's sleep/lock button decided to stop springing back all the way when depressed. I first took apart the phone believing/hoping that some dust/dirt simply got caught and that a blast of air would fix it. No luck. So I bought the replacement part.
The step by step instructions on ifixit.com are amazing. Unfortunately the replacement part didn't help. In reading other people's stories on same issue, it seems there is something missing between the button and the circuit board switch to bridge the gap.
Turns out I didn't really need to buy this part. My advice is to read other people's stories to find out exactly what you need before you buy.