The iPod case is now open, but don't separate the two halves just yet. There is still an orange ribbon cable connecting the headphone jack to the logic board.
Open the case like a book with the dock connector edge at the top, and lay the rear panel next to the front half of the iPod.
Use a plastic tool or your fingernails to carefully disconnect the orange headphone jack cable. Be sure to pull straight up on the connector, not the cable itself.
This ribbon cable is very fragile. If you are replacing the battery, you can choose to skip this step and keep the headphone jack connected to the motherboard. Prop and tape the rear case against a box to keep it in place. Be very careful not to strain the fragile headphone jack cable as you work.