1 - 2 Stunden
My PS3 (original release) finally died on me. I had a blinking red light that quickly turned to the YLOD after two days.
The repair took 3-4 hours total. I was taking it very slow to ensure I didn't accidentally ruin my PS3. The online walkthrough was extremely helpful.
The grounding wire wouldn't come out when the guide said I should remove the power switch. Don't try and force it, just continue the steps and it will come out when you remove the power source.