Replacing the rotor is very simple.
Step 1:
Untie the knots on the depower and safety lines. Then remove the stopper ball and the leash ring from the safety line.
Step 2:
Remove the rotor from the safety line and reinforce the last 5 cm or so of the line with tape. This makes it easier to slide the new quick-release onto the line.
Step 3:
Thread the new rotor onto the safety line.
Step 4:
Slide the leash ring and stopper ball back onto the safety line and secure the bottom end with a figure-eight knot (see here). And, of course, attach the depower line to the top of the rotor with a figure-eight knot.
Step 5:
Tighten everything securely and check the leash lengths again. It’s possible that the lines may no longer be perfectly matched in length.