Changing logic board to change graphic card

"You can go to the 2.9 Ghz i7 board. Apple part # 661-6589-R

It's probably going to cost you in excess of $500 to do the exchange.

I'd look to see what a brand new one is running and what your machine would bring on eBay. You will not get your money back out of an upgraded machine.

I take it you are running in Windows mode for the BF4."

The graphics card is integrated with the logic board, and all of the logic boards have the same type. You won't be able to upgrade the graphics card.