The click comes from a tiny ball bearing on a spring in the body of the eyepiece, mine popped out and disappeared when I took it apart. Immediately below the collar you just got off, the main body has a narrow grip round it with a bevelled edge, the bevel and the grip sections are screwed together so you have to hold each one and twist them to undo the thread. Once the bevelled piece comes free the grip section will slide down the main body revealing 3 grub screws. Loosen these and the inner workings should be free to slide out of the body. Disclaimer - this is from memory so might not be totally accurate, take it easy and you should be fine.