Either your video card is fried or the cable that connects your display to your card may have come just a tad loose.

I had a laptop do something similar and it turned out to be the video card had fried on it.

I would recommend getting it checked out before jumping to any conclusions, of course :D

Well, like I said before get the laptop checked out before doing anything :D

As far as replacing a video card, well, it depends on your laptop's case because different ones have different ways of getting to the components. It also depends on how good you are with your hands, whether you have the right tools for the right job :D.

I'll say this again: check everything you can or get it checked out by a professional before doing anything :D