Returning Dsi xl *Mario Kart Bundle*?

Hi, I recently bought a new Dsi XL *Mario Kart Bundle* at Walmart on Friday, December 10th , 2010. .. . *If my Dsi XL was to be slightly broken * My screen wobbles if I shake it a little bit, really lightly, it stays in place but it wobbles. My Mario Kart game HAS been opened and played. If I have the receipt , can I return it? And how many days is the policy? Thanks- Kiera..