If it's for work you take the hours needed and get it done. If it's a labor of love (your book!) then you invest the time to make it right.

If the workplace won't allocate the time, then I have to use what I do with software I re-write that is at times, a big ball of mud.

I read http://www.laputan.org/mud/ from top to bottom and it gave great ideas about fixing old bad software or documents. There is no magic to doing this work and no click a button to renumber. It's pick your plan of attack and then do it.

Since we always keep backups we are at no times limited to what we can try.
Bob