[Bolelas]

In this game the I7 wont bring you any advantages over the I5. So, get the better i5 you can (if you have the money, of course) i think it is the 3570,and 3570k, They are 3.4GHz, the K model is overclockable until 3.8GHz. Get a 3rd generation processor (starts with a 3, like 3570, 3330, 3450, 3770(I7) etc). The socket for the motherboard its the 1155 socket, and the chipset must be one ended in 75 or 77, and with a "B" or a "Z" (latest models, for 3rd generation). The P8Z77-V is a good one.

About the grafic card, i dont know much, but before buying new, try yours, it will fit on the new motherboard.
If the GT 240 wont do the job and you dont want to go for an expensive one, (like the Nvidia GTX 660, 670, 680, or ATI 7970, 7870, get a mid-range Nvidia GTX 650 or ATI 7770, 7850), they wont be perfect but i tink they can handle it in mid-settings.

I am not expert in this matter, so if anybody sees anything wrong, correct-me.