Your undivided attention for between three and 30 hours, in the first 21 days, is most of it.
Your job is to convey your information to the ghostwriter as efficiently as possible, close to the start of the writing process. This usually means being interviewed, and often providing photographs or other documents. I’m an experienced researcher familiar with many archives and libraries so if research is necessary I can do some or all of that for you.
Once you have the manuscript from me and are happy with it, you will look for a publisher or a way to self-publish; I will give you all the informal help I can. And if all you want is a firm that will print and bind your book for a limited circulation, I’m happy to lay out text for camera-ready printing.
You won’t be on your own in any case, since there is already a huge amount of help available on the internet; I can show you where to look.
You’ll be relieved to know you don’t have to write a book; but what should you expect of the ghostwriter?