I have needed to replace PSU fans a handful of times and it's very easy to do, no biggie..Use an ordinary case fan that's of equivalent, or nearly equivalent specs.

EVGA (and others) states the following, so let's get that out of the way first.

"WARNING: This unit has no user-serviceable parts inside. Opening the casing presents a risk of electrocution and will void the product’s warranty."

So if you're willing to do that and take the risk, proceed.

An EVGA 650W BQ has a Globe Fan RL4Z T1352512HH, 140mm x 25mm, 12V, 0.45A, 1200 RPM, 129.76 CFM, 38.8 dB, Teflon Nano Bearing fan it.

Take the cover screws off, then remove the cover and the fan connector (insulated-handle needle nose pliers work well)..Then the fan screws/fan.

Cut the mini fan connector off the original fan and cut the fan connector off of the replacement fan..Then splice the mini fan connector onto the new fan with the positive-to-positive (red/power) and negative-to-negative (black/ground) wires together..Separate and wrap them up in a little electrical tape..For fans without color-coded wires, here are 3-wire and 4-wire pinouts.

Screw the new fan onto the cover, noting the airflow direction arrow usually located on the fan housing..Air needs to blow into the PSU..Then reassemble.

Finally, turn the PSU on for bench testing purposes with a paper clip/wire or a PSU Tester to make sure the fan spins without hitting anything and the airflow is in the right direction..See: How do I test my power supply? in the EVGA FAQs.

You can get a good, quiet, replacement fan like a Fractal or Noctua, or whatever, with near equivalent airflow and the same or less amp draw..I just put a Noctua NF-P12 in my Seasonic unit a few months ago, can barely hear it.

Just take common sense precautions like working with insulated tools, wearing gloves, not touching/licking any circuit boards, and you'll be fine.