I have an XFX R390 card and one of the fans has stopped working. How can I go about getting a replacement fan? Is this something I can replace myself?
You will need to contact the manufacturer of the card, in this case XFX if it is still under warranty for an RMA. If it is out of warranty, there's nothing you can do.
httpsupport.xfxproducts.com/
If the non-operating fan is lubricated, maybe it works. But don't try it yourself. Someone who knows can solve the problem.