The motion to quash the garnishment is not going to be successful. You will need to vacate the judgment. That may be very difficult, and you will need to comply with some very tricky laws and rules.
The violations of FDCPA that you claim will need to be taken care of in the state court proceeding, otherwise, the other court (Federal or state) will be constrained to say that the court ruled it, so they get it.
This has many DEEP pitfalls. You should consult a lawyer who is competent in this area of law.
Mr. Krumbein is admitted to the courts of Virginia. His advice is often based on Virginia and Federal law, however, you should consult a lawyer in your geographic area for more detailed advice.