1 - 3 hours
I had replaced the front panel assembly before on this device and sometime in that I assumed I must have messed up the ear speaker during that. For awhile I just lived with it and used speaker phone or a headset but the time came to trade it in to the store for an upgrade and I had to get everything working again.
Easy repair and the iPhone works great now!
I found the iFixit repair guide a little hard to follow at the end when you're actually pulling out the ear speaker. I looked around online and found this video: http://youtu.be/AE2jj7dpIrY by a British group. They use a different method than shown by iFixit and that worked great for me.