Can i upgrade my Graphics card?

General rule for laptops is No! If you want to upgrade you need a new laptop.

You can, but you have to spend $500 dollars on the external case, then $XXX on your GPU.

Which does make it not much of a laptop anymore.

Umm i saw many videos on youtube-people changing their laptop's graphics card.. And those laptops technical specifications were lower than mine

One of the problem is getting your hands on the GPU for reasonable money, it is not something that you pick up at the store. The GPU has to have been available for your model of machine since manufacturers design the laptops/motherboards based on the specs they are going to have available for it.

You can check these out but they are for sale on ebay http://computers.shop.ebay.com/i.html?_nkw=laptop+graph...