Rotate the iPod so the black plastic tab is more accessible to you.
Use a small iPod opening tool (or your fingernail) to flip up the black plastic tab holding the display ribbon in place. The tab will rotate up 90 degrees towards the display, releasing the ribbon cable.
Use your finger to prevent the cable from lifting upwards. Wiggle the display loose from the frame, and then pull it gently outwards to release the display's ribbon cable. You may need to lift the cable away from the two white pegs that poke through it near the edge of the frame.