1. Hide them. They don't take up much space; if you try to delete them, AT&T will push them back
2. Press the $ key - see the little speaker above it
3. See 2.
4. Define fast; most BlackBerrys allow you to press the "1" (or W) key to retrieve your voice main
5. There are dozens of threads answering this. There is a New Users Forum and also an Aftermarket Forum with loads of discussions on this very subjective topic.
6. Why don't you play with it for a little while and see what you use and don't use.