Front strut/shock leaking?

Hi all,
New here. I own a 2006 2WD Titan. I figure what with the slow economy, I'll be keeping my Titan for some time to come so I'd better learn all I can about servicing it in the future.

I failed my recent inspection/renewal here in NC. The oil change place I use says the front shock has oil on it-something they've been telling me for years-so they failed me this time. It's never leaked oil or any other fluid, there are no handling or front end noise issues, etc. This oil change place doesn't do repairs, just oil changes and state required annual inspections.
Does anyone know if the front shock-part of the strut assembly- contains fluid? I'd heard it is filled with some kind of foam instead.
Thanks