Problem with fan swapping is that fans are often hard wired or use some atypical connectors. The third problem is often starting point and curve because they use DC fans and curve directly falls down on starting voltage, amperage of the fan and RPM's it has. You'd really have to find fan with same starting voltage, same RPM and same amps to get the same fan curve as original.
I've done such fan transplantation few times on my PSU's with Noiseblocker fans. It tend to run a bit slower which was fine with me since I needed quiet. It was 750W unit which never reached it's peak, meaning it never really needed more. I bought one other fan, but it didn't run well as it failed to start at low loads even though it should and I wasn't happy running it passive. But then I got the right fan and it worked great.
You can also bypass it and hook the fan on molex. This way, when PSU fires up, so do fans. And it doesn't depend on PSU fan curve anymore. Or if you hook it to motherboard and use the fan curve there. Just be careful not to forget it hooking it back on when flipping components around...