Changed Video Card and Still no display

I have a dead display. There is no faint image in the background so it's not the backlight. I purchased a new VIDEO CARD and replaced it, but still have no video. The 3rd diagnostic light is out indicating that the video card is not communicating with the board according to this link Where are the diagnostic led's on this model's logic board

Im headed to best buy to try to get a cable to try an external monitor, but im not sure what else I should try.