Hi Chris,
If it's indeed very very dark (so dark you can barely see what's on the screen) then the backlight failure might be the reason. If you're lucky, this could be caused by backlight ribbon cable slipping out of its socket. If you're unlucky, you might need to replace the whole screen (it's possible to replace just the backlight, but it's very very fiddly).
To check if the ribbon cable is the culprit, open the back of the case and carefully+slowly take it apart-be careful not to break 2 ribbon cables! 1 small ribbon (with 4 wires inside) is for the backlight. Try to wiggle it a bit to see if it's loose. If it is, open the connector (the back part flips upwards) and slide the connector back in.
You will need small philips screwdriver and good tweezers for this job.
If you need to replace the whole screen, I recommend getting a faulty camera off ebay and using it for spares-it works out cheaper than getting a replacement screen and you can resell the remains later :)
Good luck!
dupalopez
July 2009