I'm not looking to get back into a career. It's been 15 years since I last worked so there really isn't any career to go back to. I have a BA in history
(be kind please!

) and really only had one job post college--as a administrative assistant. Since it's been so long, that company is no longer in existence and unfortunately I don't even remember my former boss' last name. So basically I have no work history or references.
I'm fine with making minimum wage, no benefits.
I do have to picky about hours, as I have kids. I would really like part time (no earlier than 9 am, and I'd like to be of no later than 4 pm, but 3 pm would be better. I can not work weekends.
I would consider a "graveyard shift" if I could be off no later than 7 am
I live in the far out suburbs.
Where do I even begin? I've looked at Craigslist (probably not the best place, but since I am entry level and not expecting much over min. wage...) and found a few listings for office assistants that seem like they could actually work--they pay min.wage, but I'm ok with that. The problem is,they ask for candidates to send a cover letter and a resume. What should a cover letter say? What info should I put in my resume, since everything is SO dated--and in the case of my last employer, I don't have any contact info for my former supervisor or even just the company in general?
Thank you for any tips or advice.