Any lawyer can represent you or you can represent yourself. The key with a Chapter 7 is finding some reason why the debt would not be discharged. An ordinary promissory note gets no special treatment so unless there's something fraudulent about the filing, you cant really attack it. Did the promissory note have any collateral? Any other co-signer to go after? Did it involve a marital settlement at all? Without something special, the debt will likely be discharged.
Unless you have security on this note, such as a car title or real estate documentation, it is highly unlikely you will get paid on this note. If the bankruptcy trustee finds assets, you will receive notice to file a claim. If you have a basis for claiming that some dishonesty occurred in connection with this transaction, you may want to consult a bankruptcy creditor's attorney for advice. 11 USC sec 523 sets out reasons why a discharge of a debt can be denied - however, you must act quickly to challenge the discharge or you lose any right to complain. Hope this perspective helps!
Generally speaking a debt arising out of a promissory note will be discharged in a BK. Excepts include fraudulent statements made to induce the loan, etc. You can hire a BK lawyer who generally represents creditors but most likely that would be a waste money. You will be advised to the time and place of the 341 meeting (that when the Debtor meets with trustee). You can attend and even ask questions to see if there is something that you can pursue.