Check your MacBook's model
20 - 30 minuten
My wife's MacBook had an issue with the right fan making noise. I opened it up and cleaned the fan out, but it soon went back to making the same noise. So I ordered what I thought was the correct fan, though I did not check the specific MacBook model number. It turned out to be the correct fan by part number, but it had the incorrect power fitting for my wife's specific MacBook. I contacted the ifixit crew and they were extremely helpful in getting things sorted out for me and getting me to the page for the correct fan and setting up the return for the incorrect one.
Once I had the correct fan, the replacement was quite easy - the photo guides on the ifixit website were fantastic help (as was having the correct tools), though having opened up my wife's MacBook a total of 3 times didn't hurt either. The complete replacement process took me under 30 minutes (sorry, I did not take any pictures of the process), and now her MacBook runs cooler and much quieter!
As the title says, remember the use the ifixit website to check by the specific MacBook model number to find the correct fan for your machine - even if the fan has the correct part #, it may not have the correct power fitting for your MacBook's motherboard!