Thats a pretty broad question. What exactly are you trying to fix?
EDIT - I will base my overly broad answer on the assumption that you are trying to replace a side mount cambox on your own...
1. You dont need to worry about the switches. Those will be set from the factory. As long as you connect all the wires properly, once you turn on the machine, it will home like usual.
2. The biggest problem you will face is changing the double arm from the old cambox to the new one and then getting everything aligned properly. There is a tool for it that any halfway decent Haas tech will have but it is not needed. You can eyeball it just as well as long as you take your time. It has to be aligned to the tool pocket and the spindle which makes it a huge PITA.
Of course, I would ask why you are changing the cambox. In my many years as a tech for an HFO, I only ever changed two of them. Its pretty damn rare to have a cambox go bad...