There is no hardware nor software that can switch the screens.
Back to case mods..
That'd be hardware, wouldn't it?
Indeed. The top screen and bottom screen are both set up differently and it would require moving ribbon cables and taking everything apart to even sound feasible. After there there would be a very slim chance of it working. That's just my option, I never actually tried, but since I have a DS opened up right now and I am looking at the parts, I can tell you it would be a lot of work to swap the screens.
I've messed with it a bit and if you had the right ribbon cables I really don't think it would be too hard, if you don't want the touchscreen..
Actually, changing the video feed shouldn't affect the touch controls at all, so it would still work fine, I think.
Looking at my board, I don't think it's that easy.
Not to mention pointless for just one game. Also come to think of it, even if you did switch the screen, wouldn't the top screen (now being the touch screen) just get the same feed as a top screen and still do the same thing as the top screen? You would have to still switch that around if I am correct and make the top screen run the same feed as it would the bottom screen...this just sounds like too much work for little accomplishments.