20 - 30 minutos
The battery in my 3GS was in its last legs. It drained as fast as it charged!
The battery replacement went well. A little tentative on the take-apart leg, but full-steam ahead on the assembly (with the exception of cable #3).
Your instructions are very good. However, I think it can be improved a tiny bit regarding the detail to cable #3.
I suggest you provide a little advice to have the new installer take a good close look at cable #3 before and during it is removal. It is good to have an idea on how far it sits in place (from the factory) before it is removed. This will then give the individual an idea on how far it needs to be inserted during re-assembly. What took a little time during the re-assembly process was my uncertainty on how far that cable need to be seated in place before locking down the holding-clip. After a number of attempts, I soon realized that it only needed to slip into place just a touch (2mm) before it was locked in place.
That's all :)