If you calipers are frozen most likely they will stick in the closed position because the hydraulic pressure is forcing them the close but there is no pressure to return them to the normal open position. I don't think they're frozen...but I'm sure someone will correct me if I'm wrong.
Not sure about procedure, as far as being difficult goes but I imagine it's like doing any other strut. You can find them online for a little less than 800, maybe 600. EBAY
http://cgi.ebay.com/ebaymotors...wItem
As far as that Air filter goes, I say toss it. I never really clean them more than once and usually don't even do that. They're only like 40 bucks, less if you open a commercial account at your local auto part store.