It is a very straight forward procedure, and do it right away to prevent overheating problems. You have two choices. 1) Go to support.dell.com and enter your service tag number and order the replacement fan. If the cost is too high, go to 2) Skyline Graphics http://prosites-skyline.homestead.com/files/index.html
Dell's fans pin layout is proprietary, and standard off-the-shelf fans won't work.