Which parts should I purchase?

Which parts should I purchase?
I have a iPod 3G 40GB (Model:A1040) which clickwheel is not functioning. I can only have the "MENU" button, the "PLAY/PAUSE" button and the "CENTER" button work by pressing it hard and hold it for a while. other buttons and the wheel have no response at all.

answers:

Your first step should be to dismantle the unit and check for a physical cause, ie : perhaps a connector isn't seated properly. Corrosion could also cause this fault so look for signs of water damage.