I really need someone to help me to fully understand how to do many-to-many relationship with Entity Framework 4 CTP 5, POCO. I need to understand 3 concepts:

1. How to config my model to indicates some tables are many-to-many.
2. How to properly do insert.
3. How to properly do update.

Here are my current models:

public class MusicSheet
{
    [Key]
    public int ID { get; set; }
    public string Title { get; set; }
    public string Key { get; set; }

    public virtual ICollection<Author> Authors { get; set; }
    public virtual ICollection<Tag> Tags { get; set; }
}

public class Author
{
    [Key]
    public int ID { get; set; }
    public string Name { get; set; }
    public string Bio { get; set; }

    public virtual ICollection<MusicSheet> MusicSheets { get; set; }
}

public class Tag
{
    [Key]
    public int ID { get; set; }
    public string TagName { get; set; }

    public virtual ICollection<MusicSheet> MusicSheets { get; set; }
}

As you can see, the MusicSheet can have many Authors or Tags, and an Author or Tag can have multiple MusicSheets.

Again, my questions are:

1. What to do on the EntityTypeConfiguration to set the relationship between them as well as mapping to an table/object that associates with the many-to-many relationship.
2. How to insert a new music sheets (where it might have multiple authors or multiple tags).
3. How to update a music sheet. For example, I might set TagA, TagB to MusicSheet1, but later I need to change the tags to TagA and TagC. It seems like I need to first check to see if the tags already exists, if not, insert the new tag and then associate it with the music sheet (so that I doesn't re-insert TagA?). Or this is something already handled by the framework?

Thank you very much. I really hope to fully understand it rather than just doing it without fully understand what's going on. Especially on #3.