Do you have a LCD monitor you can access?
I would be curious to try to see if this monitor works fine from your laptops video output. If it does, then you know its something happening with the display on your laptop itself, maybe the wires in the hinge came loose or something?
But if your external LCD display does the same, then you know your laptop has the problem.
I would start there before trying to troubleshoot anything else, at least you know with certainty where your problem lies