20 - 40 minutes
A month ago, my Mac Mini 2009 became suddenly very noisy... I decided to open it up and made several tests that helped me realize it was the fan.
The repair was super-extra-easy. The Mac Mini 2009 is the last model before the unibody conception, so you've got to use some special tools (see tutorials on this website), but it's really easy and fast.
Of course, I was afraid it wasn't the fan before turning on the Mac Mini, but ... yes! now it's the world of silence, again