Alienware M17xR4 Need Graphics card help!

Hey folks, I had the misfortune of having my video card fry on me a couple of days after the warranty expired. I am trying to figure out what I need to do to get the video card replaced, so I contacted tech support and was told they couldn't help me since the warranty was expired. I then proceeded to contact Dell Parts to get prices, part numbers, and compatibility of other video cards, I had no luck with this either, as they said they had no more replacement cards in stock as well as they didn't even know what the part numbers were. So completely a waste of time. The laptop is barely a year old so I really need some help. I currently have an Nvidia GTX 675m I am hoping someone here can enlighten me as I am not accustomed to how to get parts for laptops and I know it isn't quite as easy as desktops. Questions: Are the video cards for laptops all different as one from say the new Alienware M17 or will video cards from either fit in either. What video cards are compatible with the Alienware M17xR4? Will any of the 800 series work? What are their part numbers? Where can I purchase one of these cards? Will I need to purchase another heat seek unit as well? Any other information you can give me pertaining to how this works on laptops would be much appreciated. Please let me know if you need any further information from me in order to answer the questions. Thank you