I haven't tried that. I didn't play either of the stories that came with the game. I made my own sim for the story part. Here's the official site for Sims stories, you could probably find a lot of information over there. Why it's on Yahoo I don't know, but that's where EA put it.
http://sims.yahoo.com/downloadsPS I wouldn't re-install it, I believe you can reset the neighborhoods the same as you can in Sims2. I'm firing it up now to try a different story.
Ok here is how you switch the profile to the other story or a new player. Click on shipwrecked and single, then see at the top on the right side right next to where it says sims castaways stories. It says default player, yours might say something else if you named it. There is a little head and right under it you click. Then you get a list, just click on the first name on there. Mine says default player/then click on the +/add a player profile. Give it a name to save as, then it will let you switch between stories or add your own sim for the story.