[Users] Adding openser to an already in use asterisk pbx

Hello all, I am very new to openSER and have been going over MANY, MANY pages of info on openSER (and SER) and am having a bit of a problem figuring out what exactly i need to do for what I am trying to have happen. Basically it's like this: I have a small company running a NATed asterisk pbx (there is actually about 30 to 40 users already setup and using Asterisk). Now I would like to add openSER to allow some outsourced/remote users via voip so they may dial anyone in the company directly over their voip connection. Basically, all asterisk users can call all asterisk users and also call remote (openSER) users; and all remote (openSER) users can call Asterisk users. I know Asterisk decently well, but I am not sure what I would need to set up in openSER to handle this. My Asterisk box is currently not set up for DB auth. I just have the users set up in sip.conf. Re-doing the Asterisk box is absolutely out of the scope of this project. I would just like to set up some remote users via openSER. (I do have a public IP set up for my openSER box.) Anyone have this type of setup going? Or anyone can tell me how this would best be done? (I'd love to see an openser.cfg of this setup....) Thanks in advance, Ben Jeffries fjsixty [at] gmail [dot] com