> Do I need a samba share setup?
> Do I have to manually add the hostnames
> to the Linux slave files?
No. You can use standard zone transfers to copy the information to the secondary name server.
> How could I get the two DNS's to interact
> with each other so the NT machine updates
> the Linux box?
This is automatic if using zone transfers, as mentioned above. It is all in the configuration of the secondary, if you go with zone transfers.
One warning with using zone transfers. If your secondary uses zone transfers, and the primary server goes down for an extended period of time, the zones might expire and the secondary will not have a source. Best practice dictates the secondary has it's own records. This is where you might want to consider some sort of file transfer from the NT (perhaps SAMBA might work for you here...).
> Does rndc have to be running to allow named
> to run properly?
No. This is a "controlling" type of utility. It makes it easier to update and control the name server. It is a good thing.
> What kind of security issues do I need to
> look at?
All-purpose box security issues apply. This should be done prior to putting any services on it. Best practice security issues can be reviewed at many Linux sites. Search on "hardening" your linux server. SANS (sans.org) is a good place to look as well. I have no affiliation with SANS.