1 - 2 hours
My oldest daughter had a rash of bumble fingers. She must have dropped her iPhone 10 times. It was a mess. The battery wasn't charging at full capacity and the screen began losing pieces each day. I began the 3 1/2-hour task of repairing her iPhone. She fell asleep waiting for me to get done. She woke up with her ringtone going off.
I knew going in to the repair would take some time. The guide says two hours, but I figured it would take me loner. Not only did I have to replace the screen but also the battery and home button.
The glued areas caused me some frustration and extra time to overcome. Persistence and patience are good virtues to own.
Read the little notes with each step. I learned a lot by doing this and avoided what could of become many pitfalls as well as lost and broken pieces.
Using the iFixit magnetic project mat really helped. I placed and marked each tiny piece with each step and location. I bought the magnifying flip-up head glasses to help me see what was going on.
Make sure you have enough lighting and a small towel or washcloth to place your phone on. This really helped me keep the phone from sliding and pieces from moving around.
Assembling all the parts back together took less time. Kind of like filling your pickup takes more time than unloading it.
Remember these things are fragile. Using a soft hand is a must to prevent mishaps and broken items. If something is not working, take a break and come back to it. Do not force anything. There's a reason it's not working. Just try to figure out why and you'll be OK.
iPhone 4S LCD Screen and Digitizer
iPhone 4S Home Button
iPhone 4S Replacement Battery
SIM Card Eject Tool