I want to replace the air filter

When you buy the filter ask the part store guy to show it to you, this way you can do the next one. Zee

Replacing the air filter on your 2008 GMC Acadia may be easy, or it may be difficult depending on your skill level. First you will need to disconnect the fresh air duct and the PCV breather hose from the engine. Then unplug the mass air flow sensor. There are then six screws holding the air cleaner cover to remove. With everything disconnected, you can remove the air cleaner and replace the filter. Don't forget to remove any debris you find in he air cleaner box while you have the filter out.