Guys I think you are all way over complicating this
The wiki here outlines it. http://wiki.freepbx.org/display/PHON/VPN+Setup
You dont have to download any tar files, you dont have to change templates.
Once you enable VPN for a user in user manager and have your VPN server running all you do is in end point manager you go edit extension routing and tell the extension what VPN client to use. This will rebuild the config for that phone and have it connect to the PBX using the VPN IP not the IP defined in the template.