Persistent site-to-site OpenVPN connectivity.

[myxlflik]

I am looking to establish persistent site-to-site VPN connectivity between two sites. Here is some example information for the general topology and what I am trying to do.

ISP 1 Router WAN IP: 1.1.1.1 > has a Dynamic DNS name (Example site1.foo.com)
ISP 1 Router LAN IP: 192.168.10.1
Site 1 DHCP Scope: 192.168.10.1/24
Site 1 VPN Server IP: 192.168.10.2
Site 1 VPN Server Host OS: Debian Linux

ISP 2 Router WAN IP: 2.2.2.2 > has a Dynamic DNS name (Example site2.foo.com)
ISP 2 Router LAN IP: 192.168.20.1
Site 2 DHCP Scope: 192.168.20.1/24
Site 2 VPN Server IP: 192.168.20.2
Site 2 VPN Server Host OS: Debian Linux

What I would like to do is have permanent bi-directional LAN to LAN connectivity with the 192.168.20.0/24 subnet clients all being able to connect to 192.168.10.0/24 clients and vice versa. I understand that I will likely have to run both of the OpenVPN servers in client and server mode and that I will have to put static routes on my routers to point the opposite subnet to the VPN server IP. I also realize that I will have to forward some specific ports through the router to the VPN server as well as any necessary firewall rules. I am wondering if someone had a quick howto in order to implement what I am looking to do here. I have no doubt that I can ultimately figure it out, but I admit I am trying to see if someone has already invented this wheel before I re-invent it for myself. Any guidance will be greatly appreciated.