Can use all the help I can get here to try to fix my notebook

Hi everyone

I have an Alienware M17xR3 notebook and recently the graphic card died for the 2nd time.
I bought this notebook brand new in may 2011 for about 4000$ and it has given me nothing else but grief.
The motherboard needed to be replaced, all the memory was replaced, the graphic card died and needed to be replaced, one of the hard disks failed and needed to be replaced, WiFi never worked, my battery died almost immediately, etc, this list goes on.
Since my notebook is out of warranty I called Dell to ask about a new graphic card for my M17.
Imagen my surprise when the guy from dell told me they are asking 500$ US for a card that's 5 years old ( geforce 460m).

What I would like to ask you is if it would be possible for me (with some help of you ) to buy a new graphic card and fix this myself?
I have only very limited pc knowledge and I'm not sure where to start in my search for a new card.
I sure can use all the help I can get here.
1 more thing, I'm living rural in western Australia and the nearest shop is 3hours drive away.
Thank you for your time
warm regards
Alex