1 - 2 uren
Somewhere between lazy parenting and my children preferring air conditioning to the hot sun, my PS3 logged a lot of play-time in a hot upstairs room in the dog days of summer. As a result, solder cracked, and I got the dreaded Yellow Light of Death (YLOD) on my first-gen (bulky) PS3, 8 years after I bought it.
The difficulty rating on iFixit was right: it was Difficult! They estimated 1 hour, it took me 5. I was very slow and methodical, making sure to do everything right. I was frustrated that iFixit's text guides didn't always match the video guide. For example, I was told in the video to spread the thermal paste using the hard plastic card that came in the kit. In text guides on how to spread the paste, however, I was told to put plastic wrap over my finger and spread with my finger. I found that the latter was an absolute fail: whenever you pull your finger away, you're gonna bring some paste with you, so you don't get an even spread EVER. Gotta go with the card.
Also, "follow the steps in reverse" to reassemble a totally torn-down PS3 is not helpful. I mean, for the most part it's fine, but good luck putting the plastic top cover (not the "smart cover," the one just under it). It's gonna take awhile, there are dozens of spots that have to line up.
Don't stray from the guidance with the heat gun. I have friends who have permanently destroyed their PS3s and Xbox 360s by blasting that heat gun on high, or getting too close for too long, or not waiting to let the board cool on a level surface. Also, definitely get a tray of some kind for all those screws.
As for putting that top cover back on, start at the front, angled to get those plastic brackets to line up with the bottom front. As you lower the case, make sure the left and right sides are all parallel. You have to make sure you clear the memory card and bluray areas, and then push back a bit and close at the rear.