Well, I had the same card die, at least I think it was the same, might've been BFG...
If you can push in the plastic pins on the back of the card you can pull the heatsink off, maybe having to remove some small screws on the side, but it sounds definitely worth it. Those cards are all possible to remove the heatsink, so shouldn't be impossible, then just reapply paste to the main core GPU after cleaning it off. The one I cleaned off there was Dust under the solid heatsink, which had two horribly dirty fans, Removing the dust under there is important as it insulated the chips.
I don't know if you have to repaste the chips that surround it, I usually don't, but if somebody knows otherwise, please speak up
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