1 - 2 horas
My backwards-compatible PS3 got the YLOD after 5 years of pretty heavy use.
Swimmingly! The only stressful part is reflowing the solder because I didn't know if I heated it for long enough.
Just make sure you heat the board evenly first and when you're actually aiming at the GPU and CPU, keep the heat gun really close. And the magnetic project mat made keeping track of the screws a breeze. Highly recommend it, as I had no extra parts left over at the end.