Here is what I want to do and have already done. 
I have... 
Sme Server 6 Running as gateway and server 
I set the internal address to be 192.168.0.x and the external address to be 69.8.x.x 
I only have 1 NIC installed on the box. I can only access one of the ethernet interfaces at a time. It depends on if I switch e0 or e1 around from normal or to switched. 
Is it possible for me to run both the local and public interfaces on 1 NIC? Is there a different trick to it?