Place the rear panel next to the iPod, being careful not to strain the orange headphone jack cable.

Lift the hard drive up with one hand so you can access the headphone jack ribbon beneath.

Use a spudger to flip up the plastic tab holding the headphone jack ribbon in place. The tab will rotate up 90 degrees, releasing the ribbon cable.

The rear panel is now free from the iPod.

Now to repair the damage caused by liberating the internal parts of the iPod Classic! It is highly likely that at least one of the metal clips in the lower case has been bent upward. These clips must all be pointing downward in order to reinstall the rear panel.