Northbridge fans are nothing more than noise generators. I also got a GA-8IEXP board which had this problem. So I removed the fan since I bought it 10 months ago. And the board is still working great without any problem.
If you have good in-case airflow, you can probably get away with it... but don't just disable the fan... remove it so that you get the maximum airflow over the heatsink.
If the fan is going bad on you and you want to replace it, I'm pretty sure that's a standard 3700rpm 60mm fan and you can probably get one from a computer store easy enough. 60mm fans running 2800 rpm were the standard on pentium 1 and II coolers, they're dirt cheap and a lot quieter... so you might like to try getting one of them.
The GA-8IEXP is one of the first Gigabyte mobos to have northbridge fan. Since then G'byte implements fan on every high end board. Like I said, those cheap fans are nothing but noise generators, and if you search old posts you'll see complaints from some other users on the same problem. I have no idea why G'yte decided to add a fan on its mobos. Maybe that would make it "look" fast.