[Brandon Sheley]

you can add them from the file sysytem
on the impex page for the attachments, it gives you an option as for the location of the attachments.
Upload your old attachment folder somewhere on the site, and point to it in impex when you get to the attachment module.

and ps.. you can import any size sql dump into your DB, size doesn't matter, at least around a few gig's doesn't matter, you can upload it with SSH in a matter of seconds.