You can legally prepare and file your own amendments to your own schedules. As to which forms you need to amend, you must have told the petition preparer which forms to use and where to put the various numbers you gave her -- for her to do anything except put numbers on paper in this way would have been illegal, and you should report her to the U.S. Trustee if she did anything more than that. But, since you were in control of the preparation process then, you are in control of the process now and must figure it out. Perhaps your court has a self-help page on their web site.
BTW, I don't know where the limitation to 30 new creditors comes from. It certainly is not in the Bankruptcy Code or the national Bankruptcy Rules.
Bankruptcy law requires you to list all your creditors, so adding on these additional creditors isn't an option, it is a must. In addition to filing the amendment, you will also need to mail a copy of the bankruptcy notice (Form B9A) to each additional creditor.
If the debts are unsecured, you would amend Schedule F as well as the creditor matrix. You should also submit a certificate of service of the Form B9.
Hope this perspective helps!
You do need to amend, or you risk the possibility that the debts will not be discharged. You would do better paying an attorney for assistance, as the petition preparer cannot give you legal advice, and if she does she is violating the law (and more than likely WRONG). Bankruptcy is an intricate maze and relying on someone who is uneducated could very well get you into worse trouble than failing to list some of your debts.