You should review this article on your rights under the FDCPA.
If they file a lawsuit, you will be served with legal papers indicating the nature of their claim and how long you have to respond. If you fail to respond, or lose in court, the court will enter a judgment against you for the debt, court costs, and possibly their legal fees. They will ordinarily seek to collect the judgment from your assets. If you petition the court, you may be permitted to make installment payments.

