Is it okay to repeat core findings of a cited work in detail?
When you say "core content" I'm assuming you mean the conclusions and, perhaps, something of the methodology. The "findings" of the work. 

If you properly cite the other work, you aren't copying it. You can quote it or paraphrase it accurately, so long as it is cited. But your basic inclination to be complete in this case seems correct. This is especially true if you need to interpret (and justify the interpretation) of the other work(s) in any way. If your readers need to make their own interpretations, things might be more confusing to them as well as being painful to have to find and read the other papers. 

I'm assuming, of course, that a reader of your work won't need to actually completely digest the works on which you base  yours.