My PS4 had been running very loudly for some time. It definitely sounded like a hair dryer. I had been keeping it a cabinet with a glass door that I left open when it was on. Sometimes we forgot to open the door. Recently, the PS4 has shut itself off due to overheating and does this frequently now. The final straw was when the fan made a loud, agonized sound and stopped.
Looking around on the web, it seemed pretty clear what the issue was.
I followed the step-by-step instructions, and it went very well. Removing the power supply cable took quite a bit of force but everything else went smoothly. The existing fan had a lot of resistance--it would slow down and stop quickly when spinning. The replacement fan was much better.
I cleaned off the existing thermal paste and applied new paste following iFixit's instructions. The reassembly went much faster than the disassemble. I just followed the instructions in reverse order.
I fired up the PS4 in its new home in the open air-not in a cabinet, and it is running quietly and without error.
I have never done a repair like this before, but it was straightforward with the right tools and instructions.
Do not put your PS4 in a cabinet. It needs ventilation.
Have an assistant in case you forgot to have everything at hand.