5 - 10 minuten
I know it was the fan because laptop was running a lot warmer than before and was making loud squealling noise.
The repair was so easy and fixed the issue.
I recommend getting the Spudger. If your not sure about the screw drivers order the two they recommend. Be careful about the case screws they are real tiny and two different sizes and I'm not sure where to get them. The fan screws are just as tiny. The case screws appear to have lock tight on them from the factory and I also recommend using some when reinstalling. My other Macbook pro was repaired by Apple and three screws have backed out and are lost. They didn't use lock tight when reinstalling.
Take the opportunity to clean the computer of dust including the vent holes on the case. While in the computer notice how easy the hard drive and battery are to replace. The track pad is right under the battery.
The instructions on this sight are right on. Taking your time twenty minutes is enough time to complete the replacement and cleaning.