I have to admit, while individually I knew things about both those icons, I was not too aware on their shared (his)story. So while others, you(?), may already be in an advantage considering the focus of this documentary, I don't think it was bad not knowing much. I had quite a few moments during the movie, that felt ... well a lot of feelings actually that I went through. And I reckon the same will be true for you.
Sometimes you wonder, why or how some people who are/were meant to be together, help each other out, have issues with each other. So this is not just some good feel thing you are about to watch. A lot of animosity, a lot of other things will come forth. Again, you may be aware of many of them (or most of them), but it is really well told and edited. It makes sense for those not too aware of circumstances ... like myself.