well I can't really help you with configureing solaris as I have never used it, but if you have FTP, telnet, and ssh running on the sun box then you dont' need to port forward since its not behind the router. As far as enabling DHCP, it depends if your sharing files. If you sharing files behind the router then I would use static IP's otherwise, you'll have to remap network drives everytime you restart the computers.

For network security toolls may I suggest Nmap http://www.insecure.org and Languard http://www.gfi.com