I would probably be more concerned with the return OF your money, not the return ON your money.
In Missouri you cannot charge interest...unless they agreed in writing up front. Since you have a judgement, if you can find out where they bank or if you have and old check in your files from them....you can go to the court house fill out a garnishment form. It's around 20 bucks here and the sheriff serves their bank within a day or two and they watch the account for 30 days to garnish the funds so see if they ever have enough in their account. I have only had to do it once and by the time the garnishment was served to the bank, the ex-client had already closed up shop, so I was SOL. Good luck!
Not for sure, but, I doubt it. You'll still get lucky if you get paid. I think you have to take it back to court to garnish the wages of the person/client that didn't pay you. Sad but probably true. I won't extend a client credit until they prove credit worthy at this point. In my career I was only not paid once before I learned that lesson.
It's funny cause the douche has owed me $600 for 3 years for 2 appraisals I did, I saw him in a bar the other day and he fled before I could confront him.