Most if not all after market coolers will fit reference PCBs, with that in mind it should be easy(Think CPU Heat Sink Fan) to replace the sock cooler. They should come with a VRM sink and memory sinks, which stick in place with preapplied thermal tape or pad. Just make sure you clean ram chips and vrms with Denatured Alcohol to avoid them not sticking properly and falling off!
I like this one, it will take up 3 slots and cost you about $70 but run cool and quiet. http://www.arctic.ac/en/p/cooling/vga/376/accelero-xtreme-plus-ii.html?c=2182