I have 5100 for almost a year. At the begining there used to be more air coming out through the vent when fan run in high speed. But now much less air comes out even when fan runs in high speed. So I feel its time to clean the heat sink.

How do I clean it? Do I need to open up the system or just use the vaccum cleaner to remove the dust out? DO I need to clean anything else?

Any help would greatly be appreciated.