No, that is not a video card issue. Try an inverter first, they are cheap (check on ebay for your model) if you can do the work yourself. Then can try a new LCD screen or backlight.
In some cases, it may be easier to buy the whole top assembly with the lid and screen already together, so you just have to remove the whole thing and screw the new one in. Simpler than cracking open the whole thing to remove the screen, although since those things are sold used, there is a chance the buyer is selling a bad one. Like with anything used you get without testing first.
To test the external monitor, hook it up with the laptop turned off, attach a mouse/keyboard to it if you want. Turn it on, and immediately close the lit. The default screen will go to the monitor in this case.