Howto configure Virtualbox networking?

[mildmanneredreporter]

I put virtualbox 3.1.2 on a Ubuntu 9.10 desktop, on a Pentium 4 machine with 1 built in NIC and two PC card NICs, ID'd as eth0, eth1, eth2.

Goal: Run pfsense as home firewall and Ubuntu server as file/print server, both as VMs, save $150 in electricity a year.

So far: Installed and got running both instances.  But no connectivity. Totally baffled by various interface protocols. No idea what Virtualbox networking settings should be or how to configure machine settings. I need to reach my pfsense LAN via host, have VM Ubuntu server on same LAN subnet.

Combed through Virtualbox guide and this forum, still baffled.

Any insight you might offer?