2 - 3 hours
I fixed a friends screen on her 4S. In doing so, I managed to slightly tear the ribbon cable of the power cable. Fantastic.
I bought the part and had it sent 2nd day air. The tear down is a breeze. Reassembly took a bit longer. Folding the cables of the new power cable took a bit of work.
Be careful during the removal of the light/proximity sensor.
When removing the speaker from the old power cable, try to keep the sticky foam. I lost every bit of adhesive and used a TINY bit of superglue. The front camera retaining clip takes a bit of force to remove, and was a pain to put back on correctly. Just take your time and follow the steps. Don't rush anything!