I'm in a good mood so I'll answer your question instead of making you search for the answer!
Yes you can transfer the dl game to a sd card, but you can't play it from the card, it must be on the internal wii memory. Even if you accidentally delete it from your Wii, you can redownload the game again for free, nintendo keeps a record of which games your console has downloaded. You would not have to buy the game again.
Hope that helps!