You should contact an attorney immediately with this. Getting a judgment vacated is difficult, especially with the passage of time (but there are ways if the original default was not obtained properly). Most litigation attorneys will offer a free consultation and you should take what paperwork you have to one and get their opinion as soon as possible.
Legal disclaimer: The answer provided above is for general information purposes only and should not be relied on as specific legal advice. This answer does not form an attorney-client relationship. You should consult with an attorney of your choice to fully advise you about your legal rights and obligations.
It is unusual that you didn't know that you were involved in a lawsuit. Before they can get a judgment against you, they need to serve you with the complaint and a summons. If they didn't do this properly, you have a leg up on getting the judgment vacated.
I agree with my colleague, you need to get a lawyer NOW. While the judgment against you is probably void if they never served you with the complaint and the summons (I am assuming that because you seem to be surprised that there was even a court action), the longer a judgment is in place, the harder it is to have removed. DO NOT DELAY. Search Avvo for a local lawyer who does this kind of work, even my colleague (he does seem to have an interest since he gave a good answer).
As stated by the others, the failure of service of process on you would invalidate the judgment. You need to check the court file to see what notice of service of process is reflected in the file. If nothing is there, or it is forged, the judgment may be vacated. Call me or another lawyer as soon as you can.
There is a procedure to vacate a judgement under Civil Rule 60. Certain options expire after a year. However, if it can be proven you were not served, and you have a valid defense, you should be able to get this set aside. Get a copy of the summons and complaint, and a copy of any proof of service that was filed (by a process server), then take those to a lawyer to discuss your options. I have handled a number of motions to vacate default judgments and would be happyt to talk with you.
Posts on this forum are intended for educational and information purposes only and do not create an attorney client relationship. The answers posted should not be treated as legal advice. The posts are intended to be accurate but are based on incomplete information and may be truncated for expediency or to avoid disclosing confidential advice on a public forum. They are not a substitute for speaking directly with an attorney in your area. Mr. Thayer is licensed in Washington state only and laws in your jurisdiction may vary.