My Screen is becoming detached from the key board...kinda

This is hard to explain, but one day a couple of months ago when I was opening up my computer I heard a cracking noise. It actually turns out that the left (if facing the computer like you are using it) 'hinge' covering had cracked off due to the dislocation of the 'hinge itself. i know that the part in question must be fixed by Apple, but just today when using my computer The screen will go black at a certain point of being opened or closed. I am afraid that I will not be able to use my computer for much longer, and I am about to start back at college for the fall semester, so this would not be the most convenient time for my computer to stop working.

I was wondering if this had happened to anyone else, and if so how much would the repair cost??

Thank you.