Macbook Black Screen Rehash

I have a Macbook I got 2nd hand on adverts.ie. At times, the screen goes dark and I can't see anything on it although it's still running away but it can be rectified by physically closing the screen and opening it again several times and it usually brightens up again so I'm not sure if this is the Macbook Black Screen of Death that a lot of people seem to have had problems with.

Recently, the problem seems to be worsening and no matter how many times I open and close the screen it remains dark (it will remain bright when I close the screen physically and reopen it up to about a 90 degree angle of screen to keyboard but when the angle of screen to keyboard exceeds 90 degrees it goes dark again). Difficult to analyse the problem over a forum post but anyone got an idea how much something like this would cost to repair?

Just a few points in relation to the laptop copied and pasted from System Information
MacBook 13-inch Late 2007
Processor 2.2 GHz Intel Core 2 Duo
Memory 4 GB 667 MHz DDR2 SDRAM
Graphics Intel GMA X3100 144 MB
Serial Number W8745194Z64
Software Mac OS X Lion 10.7.5 (11G63)