Have I broken my friend's camera...any advice?

[Overread]

The viewfinder is supposed to go black when in live view mode because the mirror inside has to flip up (thus no light reaches the viewfinder) in order to activate the sensor to show the liveview image.

Also have you ensured that you've tried changing the AF point itself to a different AF point in order to make sure its not just that you've re-assigned the AF point as suggested above.

 

[KmH]

There is little doubt that the phase-detection portion of the auto focus system is AFU.

Either the secondary mirror is askew, or the splitter for the phase-detection AF module has been jarred out of position