Today I changed the PSU fan from the ball bearing one in the unit, that sound like an aeroplane engine, to one I ordered from Amazon with hydraulic bearing.
I ordered the 3510 /24vt made by Winsinn.
Came in a box of 5, so if it dies I have spares.
To change, pop out the 5 hex screws holding the back plate
Pull out the connector for the fan.
Take the new fan and swap the pins red/black using a pin to release the connector from the white plastic holder and then reinsert the other way round.
Undo the 4 hex screws and bolts holding the fan on the back plate and replace the fan (same orientation).
Plug it back in to the board.
Replace the back plate.
OMG I can hear myself think.
20 mins start to finish.