It is impossible because your graphic card is integrated in to motherboard. It is only possible to swap it in G75 but only with updating a cooling system of GPU. Also to get better performance in games You can switch a resolution in games from 1920x1080 to 1366x768 this will give you some boost in FPS! And a little overclocking is possible like here: http://www.youtube.com/watch?v=yQUiYfK6uj4
Asus G74SX> Asus G55VW 3D> Asus G75VW 3D> Asus G750JW> Asus G750JX> Asus G750JH
Thank you. The reason I was looking for a new card, according to ASUS tweak, my GPU runs at 92C when I am playing Ghost or Battlefield 4. I run them with most things set to low. I will try lowering the resolution. It runs at that temp when on a map playing, when maps are loading or in lobby it runs about 74C
How old is your laptop? Have you ever cleaned it or have you ever changed thermal grease?! I think this temperature is too high because my didn't become hotter than 70 - 75C (according to open hardware monitor or aida x64). But I changed thermal grease and installed the last driver from Nvidia off site. Try to monitor it with several programs one by one and if it's rely that hot you should clean whole cooling system and change thermal grease.
Asus G74SX> Asus G55VW 3D> Asus G75VW 3D> Asus G750JW> Asus G750JX> Asus G750JH