you shouldnt have much to worry about.
i hhave 3 cats (2 short hair and 1 long hair) that frequent the office with the macpro and other systems in there.
no fur gets inside, but it does get dusty from leaving the window open since it attracts alot of dust.
one recommendation is to make sure the fan between the superdrive and powersupply is cleaned regular.
that ne attracts alot of dust it seems, otherwsie, mine has remained pretty clean despite the few animals.
=)