>>1 I think you mean the skill and experience to draw a proper Manga, as you can be knowledgeable about anything like how the panel layout should look like.
>>3 and
>>4 rise good pints on the fact you should have a short story that will grab the attention of said artist and a rough
storyboard.
Also this should have been posted in the "Comic's" area not the art area, or maybe a link to the comic area with you're story and rough storyboard.
/saged