Since you've come this far, no matter what your reason is for taking your laptop apart, I highly recommend a thorough fan cleaning which actually requires disassembly of the fan

There are 4 small screws holding the top of the fan cover on - Don't be surprised if they are very tight. Just hold the other side of the fan with your other hand so you don't put too much pressure on the motherboard itself.

Once these 4 screws are removed, you'll be able to remove the top plate. Your work isn't done - you'll also notice that there's a piece of glued foam between the heat sink grille and the fan. Remove it as best you can, or simply cut it off (won't drastically affect results)

You should now be able to pull the grill away from the fan - you'll probably notice a thick rope of dust sandwiched inside the two - do your best to remove all of it