In the past, I went the way of 3rd Immutable Law Of Security: unscrew a few bits, take out a disk, connect it to a computer, assemble into a single-disk RAID1 array (there were two disks in the NAS, changing one was enough), mount the ext2 fs, mess with anything.
Less fun, but also significantly less terrifying (you forgot WHAT?!?). If the NAS on question were using some proprietary FS, this wouldn't work, of course.