When I was using my macbook pro 15" retina, fall 2013, the screen began to fade white and thick horizontal lines appeared. It went black wth the screen still backlit afterwards. When i restarted it it would either load and then fade and black, or it would show a loading screen and then black out or load the desktop and black out. A few days after I opened it and it went back to normal then an hour later the same problem started to occur. I replaced the screen last year when it cracked and didn't have problems until now. Could it be a graphics card? Or loose connection? Can I replace the card myself? If not how much will it coat to salvage the motherboard?