Alienware laptop graphics card upgrade - help needed!

Hi all,

I have an Alienware m17 laptop that's a few years old (2.40 GHZ, 6MB, 750GB) and was looking to upgrade my graphics card for more gaming but my technical knowledge is really limited.

My current card is a 2GB AMD Radeon 6990m - is this any good? I've noticed a slight decline in the past few years. Does anyone have any recommendations? Can I get any card or are some not compatible? Lastly if I was to get one how difficult will it be to install myself?

Thanks in advance

James