Regardless of whether or not the background would show your plea, it is usually best to answer the question honestly.
You should probably check with criminal attorney in the jurisdiction where you pled guilty, as to the legal effect of the expungement. Some states equate expungement with not pleading guilty and never having been arrested; other states do not. It is the legal effect and treatment in the subject jurisdiction that matters the most.
I would make that consultation, and then consult with an employment attorney. Good luck!
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