Hopefully they didn't let the fluidic block heater to run dry, and fry it. $2300 is ridiculous for that. Its a cheap part, and right on top and easily accessed IIRC. And if the heater was fried, they should cover it.
Agree with others, several users have reported techs not vacuuming the coolant lines after battery swap, so the lines are full of air bubbles. This leads to improper cooling and an underfull reservoir and throwing codes.
One wonders if the dealer just vacuumed the coolant lines, topped off the coolant and cleared the codes if you would be 'OK'? Not an expensive or hard job.