Replacing the fan and heat sink on your graphics card is not an easy task. If your card is still under warranty, it is recommended that you contact the graphics card manufacturer and have your card replaced or repaired. If your graphics card came as part of your system, then you will need to contact the manufacturer of your system for warranty purposes. See NVIDIA Hardware Support for manufacturer contact information.
If your graphics card is no longer under warranty, then you may wish to replace the fan and heat sink yourself. There are several local and online retailers which carry 3rd party replacement VGA coolers for graphic cards. Once you have located a replacement VGA cooler which is compatible with your graphics card, please use the following instructions as a guide to achieving a safe installation. These suggestions are provided as an aid, but cannot guarantee a successful replacement or that no damage will be done to your graphics card. Heat sinks are generally attached to the graphics card's GPU using a thermally conductive adhesive, and the adhesive can sometimes stick to the GPU. This can cause damage if too much force is used when removing the heat sink.
The following are suggested steps for replacing the heat sink:
The adhesive becomes brittle when it is cold which makes it easier to remove.
Keep sliding the credit card further underneath the heat sink to protect the GPU. If done correctly, the heat sink should come right off relatively easily.