personality, celeb, whatever?

I just got a green light from a well-known artist (who has fans on this board but I can't say) to write a book

It's one of those "as told to" biographies, kind of like the autobiography of Malcolm X as told to Alex Hailey
where it's written in first person Malcolm's voice but we know Alex wrote it

Not ghostwriting, my name will be on the cover

I'm amped but also kind of nervous. I know I can write, that's not what worries me
I'm concerned with getting (insert artist here) voice across in the correct way

tips, advice, do and don't, etc very much appreciated