Child Custody Questions

I am a mother of 1 daughter and step mother of two daughters. I am currently serving w/ the U.S.Army in Iraq. My husband is also in the U.S.Army. My husband and I have been married for 8 years. My situation is that my husband is divorced from his first wife for nine years. My step daughters are 11 and 13 years old. The divorce took place in Morehead City, NC roughly 9 years ago at that time, my husband was much younger and didn’t pay enough attention to what he was agreeing to in their divorce agreement. He petitioned the divorce because his ex-wife became pregnant by a Marine while married to my husband at the time. In the divorce agreement it just says that the children reside with their mother. Does this mean that no custody agreement was ever done. My husband pays child support as ordered by the court but has been deployed so many times that he hardly been able to see his children over the past 9 years. The mother has allowed me on occasion to pick up and allow the girls to stay w/ me even while my husband is away. Here is the problem, everything is under her terms. My husband is tired of this and tired of putting the girls thru this pain of getting them when his ex-wife allows which is not too often and she does not fulfill her promises. My husband has set up airplane tickets for the girls and his ex-wife won’t show. As of right now we reside in TN and she and the girls reside in California with her current husband who is that Marine mentioned earlier. I just need some help and assistance and don’t mean to bore you with my story, but I want to help my husband but just don’t know where to start in order to get a good Attorney for this matter.