Ultimately your method did work, I tried that on my backup version, once I had learned which objects where set to overprint (I wrote down notes as went through each path). What was frustrating while I was learning how to remove the overprint is that there are 3 settings; on with a check mark, off where it is unchecked, and neutral which has a dash and I think means some objects in the layer or group or compound path are overprint and some are not. I would select the master layer and and force it to unchecked, then I would test select a sublayer and it would be neutral again, so I was forced to look at each group/compound path/or clipping mask in that sublayer because all of them were set to neutral. Once I released or ungrouped and looked at each individual path or object, none were set to overprint. If I grouped them back up it would go back to neutral (although none of the individual paths were set to overprint). Basically, I had no way of knowing without going through each individual path. It took me 8 hours of work to do that. Oh well, I will go to press this morning. I just had to learn the hard way.
I was hoping there was a method to select object by its overprint attribute or do separation in InDesign (like I do to see if there are any spot colors in my work).
"Ah, to see the world with the eyes of the gods is geography--to know cities and tribes, mountains and rivers, earth and sea, this is our gift."