A debtor is entitled to amend a petition at any time, as long as it is not done in bad faith. The debtor must provide notice of the amendment to the trustee and any affected party, which is probably every creditor.
You can probably file a pleading page stating a notice of the schedule(s) being modified, attach the modified schedule(s) and then serve copies on the affected parties and the trustee. You may want to review the bankruptcy court local rules to determine whether or not there are any specific local requirements (because every district court has different rules for different circumstances).
Re the 341 hearing, most of the time, it takes about 10 minutes. You just sit there and answer the questions a best you can, unless you don't know the answer, in which case you say you don't know. And if you think you could be subject to some criminal liability, then you should hire a lawyer, because you need to review those types of concerns in a confidential setting.
Seriously, though, most of the time no creditors show up -- so, unless you have someone with a personal vendetta, you're likely to be there with other creditors and the trustee, and no one else (except for creditors of other debtors).
Hope this helps.
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