Blackdragon,
Would you believe I've had it done? Who would have guessed. If you've been able to read my posts, you'll find that I am beginning this journey, again.

I went through this as a teenager...needless to say, I haven't been a teenager in years.
Basically, all the muscles in the head and neck are connected. ok. And, all cranio work is, is working on the muscles and joints in the entire head...not just the TMJ. It is also about the upper spine. It is hoped that relieving the pain, tightness, and pressure there should help the TMJ.
Just make sure that if you do it, research, research and research the person you have chosen. Meditation