My MacBook fan good sad and loud. It sounded like someone down the street was blowing the snow off their drive way. Then it would over heat and power down. I took it apart on Christmas Eve. Dusted it out. Put it back together. Three months later it was worse. Eight minutes of a 42 min. TV episode is not enough. I ordered the part.
So, three months after following the iFixit instructions I gave the disassemble a second go, sans instructions. After an hour of "wait, which screw goes where" Lucinda (my MacBook) was back together. In cleaning my room this week I have found 2 screws that were missed.
Label your screws.