Hello, The clicking noise maybe coming from the hard drive. Overtime, your hard drive can collect dust, so what you can do that is really easy is use an air blower or hair dryer (must be on cool air). Use this tool and apply air between all the keys and the back of the device where the hard drive is. Afterwards, you shouldn't be hearing that clicking sound again.
Hello, It's an easy fix, when it comes to the keys. If the key is stuck, you can apply pressure to the button and it will return back to normal. But, if the key is broken then you can easily use a tool that has a a flat tip and go underneath the key and pop it out. The key will then come off and you can easily replace it with the new one. It's quite simple, you can just place the key in the empty spot and push it down and it should easily fall into place.