I don't know for sure, but I would think it's too late to DV on a judgment. They'll say the time to DV was PRIOR to it going to judgment.
Basically, by not answering the summons and not appearing to court, you've essentially admitted that the debt is yours.
However, you should be able to ask for (whether from the law firm or directly with the court the judgment originates from) all of the documents used in the suit -- including the whos, whys, whens, and how muches.
I'd also look into the details about serving. All states require (though the details differ on what's considered properly serving) that you be served prior to the court date and that you have time to ready a defense. If you weren't served properly, you could get the judgments vacated (though it leaves them with the right to file against you AGAIN later, within a reasonable amount of time -- which differs by state).
