Laura, There is one thing missing in chapter 6 and chapter 7 of replacing different FQDN scenario. The method of preparing node_prep_inventory.yml is missing in chapter-6 and chapter-7 The same is available under 5.3. This should be copied to added between existing '6.2 and 6.3' and '7.2 and 7.3' Rest of the content is perfect.
Verified with the doc link. All the required information about replacing the host is documented now