How can I reduce or expunge drug felony charge so I can apply for section 8 housing?

In 2003 I was arrested in my home for selling meth. I wasn’t really selling it. I was a user who set up undercover to meet with dealer. When they caught him they got me too. I had 2 or 3 dime sacs in bags. Anyways I was scared and pleaded no contest so I wouldn’t get prison time. I was sentenced to probation and 9 month inpatient rehab. I completed program but 7 months later I was arrested for 2 dirty tests-violating my probabtion. I was sent to prison for 90 day observation, did 2 months and got out on parole. Completed parole and never got arrested on anything again. I don’t know how to fill out petition for dismissal and don’t even remember details that far back. Can I get it expunged or reduced what do I do after I file the petition. My whole reason for this is because I need to apply for section 8 housing or low income but can’t because of that charge and I have 3 kids under 4 yrs old. I need to get our own apt because living conditions became unstable at my current address.