Try Hooking it up to an external display. See if you get anything. If not then reset the Pram, when its starting up press ( option-command-p-r) Until you hear two beeps. If that still doesn't work try removing one stick of ram it could be corrupt (but highly unlikely).
Yes and no. The macbook has liquid spill indicators (LSI) that determine if the problem was caused by spilling liquid onto the keyboard. Sadly, apple wont cover this type of repair under warranty. You can pay money to have it repaired but before you do, open the bottom cover to see if any liquid got into the case.
The first place to start would be the cable itself, it might have a kink in it therefore causing the bad connection. If you hold it in a certain position does the picture and audio come back? That would probably be the simplest way to fix it, but not permanent. Then move on to the connector itself, does it feel more loose than normal? if so, then its most likely a bad soldier joint. One more thing to consider is the contact pins might be bent out of alignment but thats probably not the case. iFixit sells Wii motherboards, but they're a bit pricy. See if you can find a Wii on Ebay for parts, and unsolder the AV connector form the bad one and put it in yours. Good luck.
Id just get a new display, but before I did that I would see if I could open it up and locate the display connector (if there is one) then make sure everything is dry and connected properly. I would also try a hard reset (opening the battery case while it is running). I hope this helps, good luck.
It is most likely the lens drive motor, or a drive gear that connects the motor to the lens could be stripped or misaligned. I had this problem a while back with a cannon power-shot. Id recommend getting it serviced, those gears are extremely tiny. But if you want to take a look inside, the repair could be just wiggling a gear back into alignment.