Nope, i tried for ages to find one, but if it's similar to my XFX GT...
1) Remove the fan power conncetion. (tricky)
2) Remove the screws holding on the front bit of plastic over the heatsink.
3) Remove the screws holding the fan on (located on the back of the card, oddly near the fan).
4) Remove the fan (pulling it out helps here).
5) Turn the card over and using a pair of pliers squeeze the plastic knobs so that they fit back through the card.
6) Gently pull the heatsink off the card.
4,5,6 are all pretty flexible if you're gentle.