Router that clients pass through openvpn tunnel (airvpn) - iptables configuration help

Hello all,

My scenario is as follows, a Linux box acting as a router. I want it to connect to the VPN client and then all the client computers on the network sending all traffic through that tunnel. I have everything setup except the iptables part. The scenario is as follows

Also if there is a better way to do this, please let me know. Maybe bridging tap0(instead of tun0) with eth1 or something. I am find with any configuration that would work.

I tried using arno's firewall and could not get it working. I do not understand enough about iptables to get it working.

WAN=eth1 (dhcp)
LAN=br0(bridge of eth0 & wlan0) (172.168.1.1/24)
tun0=openvpn

Could you guys please help me?

Thanks in advance.