No offence man, but god damn
Yes you can replace the PSU fan, I recently replaced the adda POS in my Antec with a nice Panaflow L1A. Just be damn carefull pulling that PSU open, even though it is unplugged those Capacitors (the large cylinder shaped components) will retain enough juice to knock you flat on your @ss, or even kill you if you're not carefull. Seriously be carefull not to touch ANYTHING inside your psu, and make sure it is unplugged prefferably for 12 hours before you work on it.
Also note if you fry your PSU/System/Dog/House/Self/Finger/Hand we are not responsible. Good luck.