My laptop (Acer Travelmate 8204) has started making a grinding noise, which seems to be coming from the fan (not the hard drive). Some articles online mention replacing the fan, but others imply that one should replace both the fan and the heat sink. Does it make sense to replace the fan only?

(addendum: does this procedure really take 3 hours for a noob, as this video implies? UPDATE: the fan certainly seems to be on the "top" layer when I open my laptop but some parts of it extend under other layers)

Some additional info in response to comments:

• I have run MS scandisk on the hard drive a few times since the grinding started. It usually reports finding something or other but the computer's behavior doesn't change
• I'm pretty sure it's the fan based on where the noise is coming from. I employed the cardboard tube trick from the PC World article.