I always say "There is a boat for everyone". That being said, I wonder if this is the boat for you. The engine difference should have jumped out at you, you should have a general knowledge of boat diesels, not knowing what a stern thruster is further indicates you are pretty new to boating. You could be missing other points which would jump out to a more experienced eye. The hardtop is an example, they do not weigh an awfully lot.
Most diesel manufacturers pick a color and stay with it for many, many years. Cats are yellow, Ford Lehmans are red, Detroits are green, etc.
If I were me and considering this boat I might proceed, If I were you I think I would pass.
pete