This is exactly my current setup.
Using Shibby's tomato open-source firmware with OpenVPN 2.3.2 installed onto the local gateway wireless router (OpenVPN server) and onto the remotely located wireless router (OpenVPN client). Using
TAP UDP connection, since it is layer2 all clients (wireless or wired) remotely located and connecting to the remote wireless router act as if they are connected locally into the local gateway router.
Therefore, RDP, windows files share, ect. act seamlessly with local computers interacting with the remotely located PC's behind the remotely located wireless router running OpenVPN! 😃