One of my MacBook Pro fans went crazy loud a couple months ago and started making more noise than a jet airplane taking off. One could try to make a case for it by stating that the white noise helps avoid distractions but that's not a long term solution.
So, I went to an Apple store where a "genius" told me it would take 3 days and $85 to replace the fan. That seemed ridiculous, so I ordered the fan online ($48.95 at the time) and installed it myself in less than 30 minutes once it arrived. Here's how:
This is what worked for me.
1. Power down, unplug, and remove your battery.
2. Unscrew all of the screws around the edges. Also remove all screws within the battery area. Then lift up the keyboard from the front. There are a couple latches near the front, so it helps to push back a bit against the front before lifting.
3. As you lift up the keyboard, you'll have an attachment (brownish orange) between the keyboard and motherboard. This can be disconnected by carefully lifting the connection from the motherboard.
Here is what things look like under the hood:
In my case, the right fan was shot. Of the two, it seems like it's a bit easier to deal with due to less chords overlapping it.
4. Remove the fan's mounting screws and tape, then pop it out:
As you can see, there was quite a bit of link built up between the fan and case:
5. Unplug the fan's power. This is a delicate job. Probably the most stressful part of the work. It pulls straight out with a little effort.
6. Plug in the new fan and reassemble.
1. Be careful with the keyboard. The screws removed from the outside were attached to drop down threads on the keyboard. Make sure they remain inside the case when reassembling. It's like putting a pizza box back together.
2. You can power up the computer while the keyboard is up if you keep the keyboard's power attached. This is a good way to verify that you've installed the fan correctly and that it works.
3. You'll need a some special screwdrivers. I picked up this set at Radio Shack that did the job:
In the end, I paid less than Apple charged for the repair and was without a computer for 30 minutes rather than 3 days. I'd call that a win.