I think you'd have a lot of headaches getting your games back if you sold a Wii and bought a new one. As far as I've heard only Nintendo could download the games for you and even then I think they'd want both Wiis before they'd do it.
I might delete my old data, because I have this weird quirk about other people taking advantage of my success. I always deleted my save files on rental games before returning them. Like I said, weird. I'd definitely delete the game saves, but maybe not the virtual console games.