My computer was running hot (frequently above 100 degrees) and the fun seemed clean enough but was having issues, so I thought I'd replace it.
It went great. Very easy.
You might not actually need a new fan. When I removed the old fan, I found a large dust bunny stuck between the fan and the exhaust vent. I'm still not 100% sure that this wasn't the reason the computer was running so hot. But the new fan is working great, so might as well just keep the old one as a backup.