Well, I have a geforce FX 5200... it didn't come with a fan and it runs cool.... I have a fan laying around should I put it on because I want to try OCing my card a little bit.
Well, the fact that the GeForce FX 5200 doens't have a fan shows how weak it is. I am not sure what kind of fan you have or what it takes, but if it fits and works, then I would go for it. Then again, I wouldn't have an FX 5200.
The amount you're going to be able to overclock that card without it eating itself, is so minimal you won't notice the difference, so it's not worth it. I would suggest upgrading if you're running into problems.
You ain't gonna notice it, buddy. 30MHz on a G-card is n0thing. If you're really lucky, you might render at 1 frame faster than before. And if you're SUPER lucky, you might actually be able to notice that 1 extra frame.