heater core on 1995 Chevrolet Monte Carlo

if vehicle has a/c, do i have to evacuate the system before replaceing the heater core

Book time is 2.3 hours to replace the heater core but instructions in my information system are vague, they imply the air conditioning needs to be evacuated in the labor guide but don't mention it in the repair instructions. Look at Autozone's website they have many popular vehicle repair manuals on line for free once you register on there web site.
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You do not have to remove the refrigerant from the car. the most difficult part is getting the heater hoses off outside.