3) Take care when putting the key retaining button and spring back together. They only go one way. Notice the two ends of the spring are different. One end has a peice sticking straight out from the spring - this end goes onto the gray shaft on the bottom of the case. The other end of the spring has a peice sticking into the center of the spring coil - this end goes into the black button. This end of the spring only fits one way into the button. Slide the spring in and turn it until you feel it click into place.

4) When you slide the spring over the grey shaft on the bottom of the case, note that the spring lines up with a slot at the bottom of the shaft.