If the inner lens element is cracked, one has to wonder what may have caused that defect.... I don't know how minor the crack is, but that's not a usual mode of damage. Dust, on the other hand, does not affect anything unless it's severe.
Try taking images that include a strong light in the frame. Then look for halos, reflections, and reduction in contrast.
I'm very particular about lenses, if it were mine, I'd would likely not keep either.... but that's just me.