45 minutes - 1 hour
The bottom microphone would only work intermittently so I could hear people who called me but after a few seconds, they could not hear me. Eventually, it stopped working altogether.
Ordered a new dock connector (which has the microphone attached) and smartphone repair kit and watched the video a couple of times and read the instructions a couple of times too. The battery needed some prying to get it out of the glue, and the home button ribbon cable is so tiny, it took a few tries to get it together properly. Also the main ribbon connector took some patience to get it seated properly. The whole process took about 30 minutes because I was being extremely slow and careful. SUCCESS!! It fired back up and now works perfectly. Although a bit daunting to start with, I now look back and it seems like the easiest thing to do. Great instructions - anyone can do this!
Watch for plastic sheet tabs that have to be peeled off the new part.
Order the repair kit - it has all the tools you need and the little boxes for all the screws really help.
The home button ribbon cable is small and hard to see. It looks like it lays on top of the connector, but it actually slides into a minuscule slot on the side opposite the little pop-up clamp. Tweezers were a must.
Don't force the main ribbon cable connector back on. When it's carefully aligned it will snap into place and you'll know you got it right by the little click you'll hear.
iPhone 4 (GSM/AT&T) Dock Connector
iPhone 4/4S Liberation Kit
iFixit iPhone 4 and 4S Screen Protector