loss of hot air out of the front defroster and dash vents?

The first thing to do is, when the engine is cold, check the coolant level because when the coolant is low, the heater is the first thing to stop working. If the coolant is full start the engine up and allow it to get warm then grasp both heater hoses to see if they are hot, this can tell us if it is a coolant issue or if the temperature blend door actuator is not working. Check out this guide and I have left the temperature door actuator location in the images below.

https://www.2carpros.com/articles/car-heater-not-working

Check out the images (below). Please let us know what you find.