I can't really advise on fixing the fan as I don't have experience fixing them.
You may want to replace the aftermarket cooler with something like this:http://www.newegg.com/Product/Product.aspx?Item=N82E16835186052
However at $40 for a cooler it may be worth just upgrading your 4850 to a bargain card such as a HD 7850 which should provide a considerable performance increase.
Something like this should run pretty quiet and give you good thermals:http://www.newegg.com/Product/Product.aspx?Item=N82E16814150609
Thanks for the advice, but not really looking to drop $180 on a video card. This is for my office rig, so I don't need video performance...just peace and quiet! I am looking at the 7850 for my next gaming rig however.
@unksol: I didn't think about that. I'll take a look inside and see how easy it would be to disassemble.