Trying to figure out value and identiyfy painting

I have a painting that is about 36 inx 20in, it is a large oil painting of Marylyn Monroe's face.. it is signed "Cheri" at the bottom right hand corner. From what I know, it was the LAST painting she ever did. I don't know where to go or how to go about selling or auctioning off this painting. I was given it by a friend who owed me money but now i have this painting that Im not sure how to get money for it? PLEASE HELP! i am open to any advice. is the aritist Cheri Blum?