You really don't need to replace that fan. All you have to do is this...
1. Remove NB Cooler
2. Clean Gum Off of Interface
3. Clean NB (clean it carefully!)
4. Remove 3 Screws That Hold NB Fan to HS (don't loose those screws)
5. Remove Sticker From the Back of Fan (where the wires are)
6. Put a Drop of Light Oil In the Center Where The Bushing Is (3 in 1 Oil is good)
7. Spin Fan Real Good For Awhile
8. Take a Paper Towel and Small Instrument and Clean and Extra Oil That Has Pooled In The Back.
9. Replace Sticker
10. Replace Fan Onto HS
11. Apply Some AS5 to the NB
12. Replace NB Assembly Being VERY careful not to scratch or chip the NB.
Do be very careful with the NB. Treat it like a GPU. If you chip the core, your mobo is dead. This obviously is not covered under warranty if you kill it. I've done mine once, and since then it hasn't needed it. If it sounds like a hornets nest in there, it's probably the NB cooler.