the on/off button is broken. Is it hard to replace? Is there a tech manual to help?

 

Is it physcally broken or just won't turn on? According to the service manual you must remove the airbag from the steering wheel the it's only a matter of a few screws to expose the "terminals". If something doesn't work in there, then you have to start checking the wire harness. If all the terminals work, only then do you replace the switch. If your cruise control light doesn't turn on, I think it's probably more of a wiring problem than the physical switch.

Or it could be a trouble code preventing the CC from being activated maybe? Have you plugged in a scanner and checked for pending codes recently?