Hello, can someone explain to me how to disassemble a campagnolo type cassette? I have the cassette out of the wheel but I cant figure out how to get the rings off. I bought the campagnolo tool that goes on the side but I just cant figure out how to get the things loose. Also now that I have the thing open should I replace the teeth that hold the cassette (makes the clicks)? Bike has about 20.000kms

-Thanks