How difficult is it to put in a heater core?

How do u know heater core is bad -- if no heat -- maybe u have broken "Blender"/ actuator motor - if ur not sure if heater core bad (cause doesn't leak)- then find the 2 heater core hoses - about the middle of the firewall behind engine -- both hoses next to each other - and feel each 1 - if they are both hot - then heater core is good and heat not working cause the Blenmd door is broke -- which is the #1 reason for no heat
- if u need further info -- let me know