Lift the motherboard by its top end and remove it from the laptop.

Flip the motherboard over to reveal the fan.

The screws in the next step are captive screws and will not come completely free, so do not try to remove from the fan.

Remove the five 1mm Phillips #00 captive screws from the internal fan.

Lift the fan away from the motherboard.

Refer to iFixit's guide for removal and cleaning of the thermal paste. How to Apply Thermal Paste