There is no such thing as "expungement" in California; there is a 1203.4 "dismissal" that is not a true dismissal, but which some attorneys try to convince people is "expungement," but be not deluded - your past can come back to haunt you even after that "corrective" "dismissal" is entered on your record. You should hire counsel to pull this off, especially one who will be honest and tell you that your record is not really expunged and who will tell you what is and is not gone with that sort of procedure.