Check my latter posts in this forum, another friend asked the same thing as you did.
Aw. So would it look something like this?
eth0 – 123.45.678
Eth1 – 10.0.0.1/24 (NAT’d with eth0)
eth1 (vlan74) 192.168.1.1/24
iptables -t nat -I 1 POSTROUTING –src 192.168.1.0/24 -o eth1-74 -j MASQUERADE