When you type "ifconfig -a " if you don't see eth0, it means that the network card driver is not loaded
. So either it is still compiled and located in /lib/modules/'uname -r'/kernel/driver/net and you just have to modprobe it. Or you have to find his driver, compile it and then insert it.
Once it is inserted you should see eth0 when you do "ifconfig -a". Then do:
ifconfig eth0 inet your.ip.address netmask your.network.mask up
route add default gw gateway.ip.address dev eth0