If the fan is just making weird noise then you could try oiling the bearings for a temporary fix, but if you really need to replace the fan why not cannibalize another PS4? Like buy a broken PS4 and take out the fan to replace yours.
From what I've seen around the web people can upgraded their 27" 2011 imacs which have 2400S and other S processor to non-S processors like the 2600 or 2600K with no problems, but I'm still not sure if this is also possible to do on a 21.5" imac. My dad has the 21.5" imac mid 2011 with 4GB RAM and 2400S and 6750M but he's upgraded to 8GB of RAM and now going to get an SSD upgrade and he says might as well upgrade the processor but I don't know if he can get the 2600 to work in the imac. Like I said, I haven't seen anyone tried a non-S processor in the 21.5" imac so if anyone knows if this will work please tell me. Also sorry for bringing this thread back up but this is urgent. Thanks in advance.