A bit difficult, but that is what they said!
1 - 3 horas
The left fan in my PB G4 17" was making a bit of noise. Since I wanted the computer in mostly perfect before selling it to a friend, I ordered your heat sink and fan assembly for the unit.
The repair was, as iFixit said, somewhat complex, but I was able to accomplish it and get the system working perfectly.
The pics in the iFixit's assembly guide need to be way more detailed.
There are a number of steps which relate in no way to heat sink and fan assembly. This causes a great deal of confusion.
At one point, I had to essentially ad-lib, and find my own way. The assembly guide was very difficult to follow.
But, it's done and all is well.