How to deal with writing in a difficult-to-replace book...
Write directly in the book, in pencil. Erase errors. Go over in ink later.
Write directly in the book, in the final ink. Cross out or otherwise mark errors, and continue writing.
Compose offline. Transcribe to book later.
Hire a ghost writer to do the whole thing.
Things to include in a book of autobiographical essays
An introductory summary: a precis of the timeline of one's life leading to this point, with an explaination of the purpose of the book
Essays written by one's self on whatever topics strike the fancy
Short rants on narrow, possibly ill-defined topics.
Essays written by others specifically about one, used with permission
Essays written by others specifically about one, screw permission
Pictures, maps, illustrations.
Dropcaps or Margin Initials
What style to use in essays
Whichever is appropriate for each essay