My left fan started producing some noise and so I cleaned it thinking it'll solve the problem but after some cleaning there were still some noise. I searched and found that it probably has to be oiled but the posts I've found were only for old models of MBP where the fan itself can be disassembled, mine on the other hand cannot.
But I forced disassembling it anyway thinking I could pop-off the fan cap, add some oil in it and put it back. Unfortunately with this Mid 2010 15" MBP release, the fan cap is actually attached to the spindle and there's no way on taking that off without breaking it.
Now I only have my right fan, you can't keep working properly with only one fan. You'll always on the lookout as to how much speed its running and the heat. As a developer, this means I can't run CPU intensive process as these might make the right fan give-in as well.
And so I searched for cheap and reliable apple parts retailer and found quite a few but iFixit makes the most impression. So I placed an order right away and the other week I got my replacement!
Repair went smooth, I know already how pop the fans so it was easy as a walk in the park. ;)
After plugging-in the new fan and turning on my laptop, sure enough it was detected and everything works normal.
If your MBP's fan model can't be disassembled, don't force it. Mine made an annoying sound but it was still working, by the time I forced pop-off the fan cap and tried putting it back together it wouldn't work anymore.
So a noisy fan is still better than a broken fan... at least until you get a replacement from iFixit that is. :)