In VA, go to the court house that has jurisdiction. Bring all your orders with you. You will need to file a motion for change of custody along with a motion to modifiy child support. There is no charge. You fill out the forms, the clerk will make copies of the important information, and she will be served (if she's local, it doesn't cost to have the papers served to her). At that time, you will also get a court date..I'm not sure how back logged the courts are there, but here in VAB, it's 4-5 months. Since this is the summer, and if there are problems, (which, once she gets served, there probably will be*LOL*) Then you'll probably end up back down there filing a...ahhh, I'm drawing a blank here, I forget what the form is called...it up's the court date, usually around 2 weeks from the time you file the newest motion. Then there is always filing for emergency custody (but I've never gone thru that...so..*shrug*) You can always ask when you get down to the court house. The kid is 17...I mean really, unless you are homeless or a convicted sexual offender, I really don't see much of a challenge here.
Good Luck!
KAT