From my experience, Not For Resale games aren't really worth that much. They were used in store displays around the country, and were supposed to be returned to Nintendo who are believed to have destroyed the cartridges once they were no longer in use. I've seen some of the more popular ones such as Zelda: Majora's Mask sell for around $100, but something lesser-known like Wario Land 3 probably wouldn't fetch much. I'd just keep it, especially if you don't already have a copy of Wario Land 3 because that game is awesome.