Easiest way is to peruse E-bay for 'Muffin Fans' and order one or two, probably 2 as multiple fans move more air. You want 120mm case fans, Fluid Dynamic Bearing, which are silent. Be sure to buy a 2 WIRE LEAD FAN(S). The 3 wire fans are speed controlled by a CPU. You want 2 wire only.
You remove the existing fan or fans and install the new fan or fans in the place where the old fan(s) were, wire them both together and extend the positive and negative wires to the existing positive and negative wires (that powered the existing fan). Mounting the fans will be the same as the existing mounting because all the fans (yours now and the new ones have the same mounting holes).
Your existing fan is controlled by a snap disc thermostat affixed to an outboard fin on the upper condenser and it will run your new fans just fine.
The fans will come with a small plug attached, you cut that off and attach the bared wires together between the fans and to the existing positive and negative wires.
All there is to it.
The OEM uses the cheapest fans you can get which are sleeve bearing and they make noise. The FDB fans have floating, non contact bearings and are silent (other than some very low noise from the air moving through the blades).
Real straight forward and there are literally hundreds to choose from on Flea Bay so you pick what you want and install them.
120mm FDB case fans is the key.