Quick question, any help would be appreciated.

I purchased a 3DS XL system about two weeks ago from Best Buy back when they were on sale for $179.99. Would it be possible for me to go back to the store and exchange it for the new Mario Kart 7 bundle if I already opened the one I bought two weeks ago. I would of course pay the difference, I know that much, but I have read in some other forums that systems can be returned even if opened unlike software, just need confirmation. This may be a terrible (if not dumb) question I know, but I would rather have the bundle system and the $20 gift card if possible.

Again, any help would be appreciate because the Best Buy customer service phone number is rarely any help for me.