Once my record is expunged or sealed, do I have to tell employers about it?
No, and it is against the law for employers or potential employers (except those specifically allowed by law) to ask you whether you ever had any records expunged or sealed.
BUT if you have filed for your record to be expunged or sealed and the court has not ruled on it yet, you still have to disclose your criminal history on a job application if you are asked.
Once my record is expunged or sealed, do I have to disclose it when I get an occupational license or certificate?
No, unless the law requires it. A list of regulated licenses in the State of Illinois can be found at the Illinois Department of Financial and Professional Regulation's website:
http://www.idfpr.com (This is NOT a list of licenses which will require disclosure of an expunged or sealed record.)