How can I create a status message of X of TOTAL pages under a parent?
I assuming the pages are one level down from the parent?

Parent
  | Child (1)
  | Child (2)
  | ... etc


You can do this:

{% set topLevel =  entry.parent %}
{% set totalPages = topLevel.getDescendants().count() %}      
{% set entryIds = topLevel.getDescendants()|group('id')  %}
{% set currentPageNumber = (entryIds|keys)|indexOf(entry.id) + 1 %} 

{{currentPageNumber }} of {{totalPages}}


Basically we're making an array (list) out of just the entry IDs by grabbing the descendants from the parent. Then we use Craft's group function to give us an array, grouped by key (in this case the ID). Since we know the current page's ID, we can find it in the array and return its position. Since arrays are indexed starting with 0, we just add 1 to it.