I was told by the dealer the crankshaft is.

Replace just what is broken. The engine or transmission will have to be removed to unbolt the flex plate or flywheel, but it's silly to replace the entire engine unless there is something else wrong that we don't know about. Measuring clearances and matching the correct bearings can be time-consuming. That may have influenced their recommendation. I guess I'd want to know why the crankshaft broke in the first place. They're normally pretty tough.