If you do find a mistake, carefully condense it to a find and replace set that will fix the links. BEFORE doing anything, though, backup your playlist files.
If you mainly use playlists based on ratings, I like to use a unique rating name for myself [Ben's Rating] and store that in the file itself. That way, all my ratings are saved in every file. Then, I can restore the "Star Rating" by viewing all where [Ben's Rating]=5 and rate all those 5, etc. This way you have your ratings saved in every single song. This doesn't work if you're a fan of random playlists that you just threw together.