-Do i need any special drivers? No, just the latest nvidia drivers for 6xx cards.
-Will it cause the heat in my case and in the graphics cards to rise? Nothing noticeable.
-Is my power supply enough to run both cards? Yes.
-Any other changes that need to be made?
Right click on desktop > Nvidia control panel > configure SLI, surround, physx > maximize 3d performance.
Take it from me, I have gtx 680 sli