I have played for years and I love it. I'm 5'4" and in my best and most muscular shape weigh 150lbs and I still hold my own very well. I usually play as hooker since I'm short but even in that position I come in for a helluva lot of heavy blows.
The most important things for full contact rugby are having good wind and a strong neck and legs. (Though i notice you said they were a touch team.)

It's a fun game and definitely worth getting into. I think you'd have a lot of fun playing it.

As far as what might help you, the rules on wikipedia are fairly instructive and any decent book on the history and rules of rugby should help out.

Good luck!