M1 rifles in good shape in this area are running $600-800, retail. Unless there is some state or local law that would prevent it, the best bet might be to just put an ad in the paper. If your local paper considers gun owners insane terrorists and refuses gun ads, try those "shoppers guides."
If time is of the essence, you can always sell it to a gun shop, but of course the amount you get will reflect the dealer buying rate, not the retail rate. I would call around and see what interest you get.
I would suggest a consignment sale at a gun shop, or sale at a local gun show, but with that type of sale there is no time line; a consignment item might not sell for some time, and there is no guarantee a gun will sell at a gun show.