You could take it to a local art expert or check to see if he is listed at Artcyclopedia.com
Here's one where you can create your own puzzles for friends: And these are from another site: Enjoy, they're lots of fun!
Are you sure it's an actual painting, and not a print? The print of the painting you're referring to is extremely popular. Even if it is an actual oil painting, it's very likely it's not the original. Anyways, I suggest you take a look at this post: