You can open it by disconnecting that hose clump with a plyer and taking out the PCV valve with your hand. You can check it by shaking it and hear for rattling. If you hear rattling it's fine, just clean it with carb cleaner, let it give a few minutes for it to dry and then place it back. If you don't hear a rattle, buy new.
It is often an ignored part however it is very important.