Q: If I change the primary ip address for DNS, do I need to reboot the server?
If you have a command-line only server, you'd typically:
a) manually edit /etc/resolv.conf
... then ...
b) type "/etc/init.d/network restart" (both commands as "root")
If you have a GUI, you'd just change the DNS server address and be done. The GUI should automagically do the rest of the work for you.
'Hope that helps .. PSM