1 - 2 horas
Received the Yellow Light of Death randomly one day and freaked out till I came upon this guide here. Having used Ifixit guides before, I was confident it would work. So I ordered the supplies.
Well, the guts of my PS3 are slightly different than the photos in the guide, so I had to improvise and make notes. Other than being unsure about using a heat gun and the termal pads and what not, it went rather quickly.
If your PS3 internals are arranged differently than the guide, don't be afraid. Just make notes of what you had to do differently as you go, and then reverse them when you're done. The meat of the fix - thermal paste and pads - don't change. It's sometimes just a slightly different process than the pictures.