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A judgment is good for 10 years and can be renewed when it is nine years and six months old.
Many collection agencies claim that they serve people with lawsuits when they actually don't. You can certainly go to court and take the position that you were never served and therefore the original judgment is not valid. You would be much more likely to succeed if you have a lawyer, of course.
You can also take the position that you were served too late for the judgment to be extended. There is some case law dealing with people being served in a fashion that is not "timely" even though a lawsuit was filed within the statute of limitations and the case being dismissed but it will take some time to research those and prepare a response.
You can do it yourself but you need to do a lot of research and brief the issues and this is going to be a difficult one unless you have a lot of legal experience.
There is an inexpensive e-book on legal research that is very good and you might want to consider getting it if you are going to represent yourself (which I recommend against). You may even be able to get the judge to award you the attorney's fees die to the facts.