How do gravitons impact on general relativity?

How do gravitons impact on general relativity? [...] I would guess that this kinda question was asked by some scientists and answered...

It's been asked but never answered satisfactorily. The full impact on general relativity would be that it would become a theory of quantum gravity. Nobody has ever been able to construct a satisfactory theory of quantum gravity. We have various guesses, and we can reason by analogy with other fields such as the electromagnetic field, but basically not much is known.

You would interpret this as gravitational waves being the medium through which changes in matter distributions are communicated to far away places--much in the same way that you see it with retarded potentials in E&M. If you quantize the field, (at this level) all that happens is that this transmission happens in discrete steps.

And I will say that the "medium of force" idea from QFT is an imperfect analogy. The media of force in QFT are off-shell bosons, but off-shell fields have little in common with real, physical particles.