A lot more hassle. Currently, I can continue working with the computer, accepting the occasional noise. Replacing the PSU will take 10 minutes. The current PSU does not look to easily dismantle, so that'd take a few minutes to remove it, then work out how to dismantle it, and remove the fan, if possible. It may be glued in position, or have other tamperproof fixings. Once out, I've then got the issue of trying to identify it, and match it to a replacement, if I can find one, with enough detail to confirm it is correct. Then wait for it to arrive, without a computer, unless I rebuild it to do the whole job twice. More trouble that it is worth.
Once replaced, I may look at it to see if it dismantles, but without too much enthusiasm. I still haev teh PSU from the computer I scrapped in 2015, when it was replaced with this one. Despite claiming to be ATX, it has all the wrong connectors, so won't power motherboard or HDD. Difficult to work with just a DVD drive adn no motherboard. That PSU does not come apart unless welds are broken, so no chance of using just the fan.