When you say Macro-Planar 120/4 I assume it is a CF? If yes, then this would be a good price indeed. Was the 80/2,8 only C T* or CF?
From personal experience, Ive found the 120mm to be more suitable as an environmental portrait lens than the 80mm. It is heavier and bigger though... I would take the waist level finder too, since lugging around the prism can be tiring.