If the card works fine, except for the fan, I would oil it and see what happens. You could possibly buy a replacement fan also.
I think a fan wouldn't cost much more then shipping charges to RMA the card (unless MSI will prepay you return label). With RMA's you take a chance on getting a defective card back, and having to go through the RMA process all over again. However, I have not seen many horror stories about MSI RMA's, so it could go silky smooth. In the end it's your call.