I'll give it a go.
My understanding of Chin-Na is that it focuses on joint manipulation techniques, rather than kicking and punching techniques (altho these techniques may be combined with Chin-Na in application). So the finger-locks, wrist-locks, arm-bars, shoulder locks, etc. that are found in Chinese arts are part of the body of Chin-na. Most Chinese arts have these techniques to some degree or other. Some focus on these techs alot, others not so much.
I have heard it said that Chinese Chin-Na is the foundation and origin of arts in Japan that use similar techniques, like Jujitsu and Aikido. This may be true but I am not advocating one way or the other.
Dr. Yang, Jwing-Ming has numerous books on Chinese martial arts, including a couple on Chin-Na, I believe with a tai chi chuan focus. I have seen his books at Borders, or Amazon would certainly have them. These books would be a good source of information, but if you don't already have a solid background in these arts you will probably have a hard time actually learning the techniques from them.