If you have a felony conviction on your criminal record you're not eligible to buy or posses a firearm in any state, let alone get a FOID card is this one. Yes it needs to be expunged if its not already. The people who issue FOID cards are the ISP, they are not an employer, they are the state police. Its gonna show up if its on your record. Not sure how IL works but some serious juvenile crimes like a felonious firearm charge may not be able to be expunged. Seek actual legal consul would be my advice.