Is the motherboard and video card integrated?

Hi I have a asus X751M laptop. my laptop screen is black. Ive tried pressing all the buttons recommended and also removing the battery and all that jazz. It does not work with an external moniter. The lights turn on when powered up and charging. You can hear a a humming when powered up. I suspect it is the video card. However, I took it into a repair store and they told me the motherboard and video card is integrated in most laptops. If I had a proper diagram and instructions could I replace the video card myself? He said it would cost 300 or more. I may as well buy a new one for that amount. But I cannot afford either of those options at the moment. Alternatively could i purchase an external usb video card plug it in and it will magically work? Thanks.