Fixed a sick cow of death fan in my 2011 17" MBP
The fan started groaning like a sick cow about to die or give birth—pick your poison.
Extremely easy. It took longer to remove the tiny screws on the bottom of the MBP than it did to replace the fan.
Line up the screws in the order they are removed. You don't want to mess up the order. Be sure to have a very tiny star shaped screw driver. Most of mine were too large for the fan screws, but I eventually found one in a tiny screw drive kit I bought a long time ago.