I need a Word document 340+ pages long formatted with appropriate and varied headers

I am in the final stages of getting a paperback novel ready for publication. I usually have blank headers for the first pages of chapters, and otherwise one header text for left-hand pages and another for right-hand pages. My Word program is misbehaving and won't do this. I tried copying the text only, without formatting, into a blank document and that didn't help. Neither did uninstalling and reinstalling Office. I need a real Word guru!