Display is black / blank but appears to be lit up (works with vga monitor or hdmi tv output though)... Is the LCD broken or the GPU? Inspiron 17R SE 7720

Hi I went to turn on my computer the other day at a hotel while on a job... It was a cold boot, from a previously fully shutdown system. (I have hybrid boot turned off on my Windows 8 as well [not 8.1, didn't get a chance to upgrade yet])

Unusually I didn't see anything come up on the screen besides it lighting up a bit, and I can adjust the brightness level with the fn + plus brightness and fn + minus brightness keys... But again I don't see any image on the screen at all...

I plugged it into a monitor or hdtv through hdmi and start it up and I am able to see the screen when Windows boots enough to the point where it sends that display output through either VGA or HDMI / or both...

As you can see, it seems the nvidia card is working and im able to play a game with it using the external monitor, so Im not certain what the issue is...

It's on the duplicate setting just look:

I'm prepared to buy what I need to fix it and do it myself! I just need help figuring out what it could be... I don't want to replace the motherboard if its the LCD for example!

And that reminds me I should try that LCD test diagnostics thing right now... By booting up while holding D key, and post back my results....

Its possible that while traveling in the work vehicle heavy objects could have bumped into it causing the lcd or something to go wrong...

So I'm not 100% sure that it isn't related to this issue that was just solved for me... (Just as my warranty happened to run out too haha) :)

http://en.community.dell.com/support-forums/laptop/f/3518/t/19498450.aspx?pi239031352=35

So what could it be? Do I have to replace my whole motherboard with its built in nvidia gpu and if so wheres the best place to buy one for this particular model? I couldn't seem to find a way to purchase one from dell directly...

Or is it the LCD and not anything else because everything else appears to work as long as its plugged into a monitor or tv through hdmi?

What can I do to find out the issue with certainty? I'm going to try that diagnostics test and see what the results are and post back...

EDIT: Okay so, I shut down then once it powered down, I held the 'D' key as I pressed the power button and I saw colors! So I suppose that means the LCD is actually okay? Because otherwise it wouldn't display anything / display improperly with that test right?

Could it be somehow that the video card is somehow not displaying to the built in monitor? In device manager next to the one I can recognize is my monitor is a generic plug n play monitor (the laptops screen)... It says it appears to be working normally in device manager for it also.

So if I just throw a new motherboard in there take my cpu out of this one put it in the new one properly and be good to go again? I should use arctic silver thermal paste if I do that right?

Thanks!