You're going to need another ethernet card for the second ip range. I'm assuming that eth0 is built in and that eth1 is an ethernet card.
Even though you need a separate card for each ip range, if you have a firewire card installed, you can set that up as eth2. You would do that in mcc. While you're in mcc, make sure that you have webmin installed.
The best way to set things up is by using webmin. Open Konqueror, and in the address bar, type:
https://localhost:10000
and it will take you there. You should have all your hardware installed first.
Michael