How do I replace the Fans for CPU and GPU?

Watch this video.

The procedure for replacing the SSD, RAM and CPU/GPU fans is essentially the same - disconnect the motherboard and flip it over. Once you have flipped the motherboard over, there are some small screws holding the fans to the heatpipes. Disconnect those and the wire connections to the motherboard and you will be able to remove the fans.

A few gotchas:

(1) Pay attention to how the wires are routed from the fan to the motherboard. I inadvertently crushed one of the wires while screwing the motherboard back in on reassembly.

(2) Make sure the fan wire connectors to the motherboard are firmly snapped into place.

(3) Reconnect the wire for the left speaker back into the motherboard before making any other attachments or replacing any screws. There is a small piece of plastic on the housing that will prevent you from reconnecting this wire once the motherboard is in place.