4 not connected black wires at power converter

It could be more work to change out the whole unit.
If your rig is equipped with a transfer switch it could be mounted to the back of the converter making it even harder.
I personally would go with the upgrade as long as the rest of the power center is in good shape.
Call Randy at Best converter. He has more insight and great answers.
This would be a good one. Check prices on Amazon.
Converter upgrade