Already have.
i did a RMA on my Enermax 850w to C&J Computers who do the RMA in the UK,and they sent me out a new PSU but it had a fan blade snapped,i got in touch with them and they wouldnt swap it they said i had to send it to Enermax German headquarters,ive done RMA to germany before and had to wait months so i thought it be quicker to replace fan.
it wasnt that hard taking it out as the 3 wires wasnt soldered but had a 3 pin connector on it.
Not that its hard, its just dangerous.!
But if you want to do it, just go onto a well known auction site and type "3pin 80mm fan"
Simples
Now that the OP has opened it, Thats all null & void.if they sent it you and the fan blade was snapped on arrival then it's law that they replace it as they gave you a item in return which was unfit for purpose.call them and tell them this. If they refuse then they are in the wrong how long have u owned the psu