20 - 30 minutos
Phone would die at 50-70% battery when running power hungry apps, like GPS, facebook, etc.
Repair took about 20min, being careful and following the guide on this site. It is not an easy repair, but definitely doable with the guide and being careful.
Before buying the battery from ifixit, I bought a $5 one from ebay, which didn't work. Glad I bought one from this site, works like a charm now.