Depends on whether your 401k is a qualified plan. If it is, it should be exempted.
Check your state's NON bankruptcy statutes having to do with exemptions. Most states have non-bankruptcy statutes which allow debtors to keep things like pension monies, disability money, etc. Generally, the process is: the sheriff will go to your pension manager with papers giving him the right to seize your property to satisfy the debt. When the Sheriff seizes it (or before he does), he must provide you with an application to claim your money as "exempt." If you fill that out and file it with the court where the judgement was taken and the court approves it, your money will be safe.
If your 401k is a "qualifying plan" (i.e., meets the requirements of Section 401(k) of the Tax Code), then your 401k plans should be exempt from execution.
Your judgment creditor may nonetheless attempt to levy on your 401(k) account, and you will need to file written objections to that execution, claiming the exemption, with the Sheriff to whom the writ of execution issued. Don't delay in the filing of objections, as I believe you have only ten days to do so.
Have you considered an appeal from the judgment? To procure a stay of execution pending appeal, you may need to file a supersedeas bond.
