Onan 4000 RV Generator, Code 32. $5000 Dealer Estimate!

My Onan 4000 generator died and wouldn't crank. It was so seized up that the starter motor started to smoke when trying to crank it. A 'Code 32' was raised which states that it is either low on oil or the battery doesn't have enough cranking power to start it for more than 2 seconds. I took it to the local Cummins dealer and the authorized Onan service department gave me 2 spectacularly high estimates; one for a repairing the unit and one for replacing it with a brand new generator. The technician somehow came up with these NOT free estimates without even pulling the cover off. The actual issue and the cost of the repair parts (I did the labor myself) are revealed at the end.

[@Rollout001]

Is there a reasonable justification for these two estimates? They leave me with a lingering sense of doubt, as if I were being sold a bill of goods.