1 - 2 horas
My 60GB PS3 that I've owned for the better part of a decade decided to crap out on me one day.
The repair took me two hours or so, but the time was well worth it. The repairs took and to my knowledge the system still works.
The only thing I would suggest is finding a disassemble guide for your particular model then use the guide on ifixit to do the actual repairs.