1988 Buick LeSabre - Replacing heater core

I am losing radiator coolant in the passenger side of my car and was told I have to replace the heater core. I purchased the core and was about to dive into the mess when a friend informed me that it is connected to the air conditioning system and that it had to be professionally done. I have read my Haynes manual and it implies that I only have to deal with the heater core - not the air conditioning - help!

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Welcome to AF, check this link http://autozone.com/servlet/UiBroker?ForwardPage=/az/cds/en_us/0900823d/80/17/f9/21/0900823d8017f921.jsp

Thanks for the incredible turnaround time on this!