As I'm not a sound guy I can only offer what i know, the Shure SM58 is a vocal mic used for live music, I'm not sure if this is the type of mic you're looking for if trying to record dialogue. Another thing to look for with a mic is its pick up pattern, weather its directional or omni-directional, there are many different types of mics for different situations. Any mic you look at in you're price range will be about the same quality its what you want to do with the mic that matters, shotguns are very directional and good for dialogue usually. As for the minidisk player as long as you are recording to PCM audio, you're keeping the sound "uncompressed".
Brett