I don't know that particular NAS, but does it allow you to setup an anonymous SMB user?
If not, then setup a normal SMB share on the NAS and mount it on the CentOS server, then rsync the data across
Moving the data is the easy part.
The problem here is that currently SMB runs on the 5.3 box which is also where NIS runs, and people authenticate from there.
The ZFS appliance is going to be the new home for SMB but it does not have a native authentication system and seems to want a pretty elaborate one, not something nice and simple like the Linux Samba software.