Custody Modification in Florida

My question involves a child custody case from the State of: Florida. Mother received custody of kids (twins) through divorce in 2004. The mother abandoned children and moved out of state. Because of the abandonment I never got custody turned over, figured she left, why would she want them back?? So there is a current order against me. It's been 5 years since I've had sole custody of the kids (minus a few weeks in the summer, i'd let her buy plane tickets for them to see her). She has sent, maybe 300 in support over these 5 years. This summer she kept our son, sent back our daughter but kept our son (teenager). He wants to be up there, it sucks that I get hurt because she left and he wants to see her, but he's been hurt and I know he probably needs this. I've reopened the divorce case, filed a modification of child custody and have a hearing soon. I know that in the divorce it says we can't leave the state, i'm hoping that that's grounds enough to get custody. But I have this sickening feeling that she is going to have an attorney and I won't and because of the legal jargon I won't be able to win my case. I need to know what special things I should be ready for if she does have an attorney.

Thanks for your help.

Also, I know this is the wrong thread but what steps do I need to go through in order to get back child support?

Okay... so the judgment says that she has custody, despite that order you have had custody for five years, now one child wants to live with mom and the other child will continue living with you, and you want to modify custody to do what? To simply reflect the status quo? Why do you believe that mom will oppose the amendment of the custody order?

You should not expect to get back child support, as you chose not to pursue support in a timely manner. I expect that a court will be reluctant to look at child support prior to the time of your present petition for modification.