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It's difficult to replace the cap because they are almost always non-labeled. I would just clean it up with some alcohol and try to solder it back on if it isn't damaged. I'd clean the remainder of the board with alcohol as well.
If it's damaged:
I would strongly advise against replacing it with anything other than the rated cap. If you have a capacitance meter, you could possibly get it working by measuring the old one and replacing it with a matching capacitance because ceramics usually are within the KV range. Never replace it with a random cap... You'll throw off any potential triggering/impedance/OVP that cap was used for.
I'm an electronics engineer
Any 0805 ceramic cap will do its job, anywhere from 100nF to 1uF is OK decoupling, you could put a 10uF 0805 since they are now common, just remove one cap with the same size from another GPU and you are done, the problem is that the pad is ripped, with care you can remove the soldermask from the via that is half intact and solder the cap to the via, maybe tombstoning the cap in the intact pad and then a wire from the via to the other contact of the cap, and brush the surrounding area, it seems strange/dirty.