Insert the pointed end of a spudger into the leftmost slit at the top of the antenna case, where you previously removed the circuit board

Once the spudger is inserted into the leftmost end of the slit at the top of the antenna case, slide it to the rightmost side of the slit.

Slide the antenna case out slowly or you may lose the antenna's spring. The spring is inside the black plastic that holds the antenna case to the device.

Slide the antenna case out of the device.

Reinstallation tip: first reassemble the antenna casing (place antenna back into its plastic cover), and then re-insert the entire assembly back into the GPS body.