It sounds like a simple question, easy enough to answer. Unfortunately, this question will get you nowhere fast (unless you like getting sweet talked by opportunistic attorneys who are more interested in making a buck than solving your problems). To get a helpful answer, ask whether you SHOULD sue.
Most people roll over and give the bank everything they want after being served with a foreclosure complaint. With the right strategy, and the right attorney, you can realistically stay in your home months, even years longer than you might think.