This is one of the easier disassembly guides for this device. The case is easily removed, but will void any still existing warranty on the device. Removing the case is necessary to get at any internal component.
Pry 4 plastic feet off the bottom of the enclosure using the iPod opening tool.
Unscrew the four screws previously covered by the feet.
Flip the device right side up, then gently slide the casing upwards and off the hard drive.
Flip device upside down again.
Gently pry the bottom gray casing away from the device.
Rotate so back of device is facing you, then gently pry the back casing away.
When back casing is removed, the fan will become loose.