You will need to remove the dash and HVAC housing to access the heater core.
Start with disconnecting the battery.
You will then need to recover the Freon from the ac system and drain the antifreeze.
Under the hood you will need special tools to disconnect the ac lines at the firewall, remove the heater hoses, remove the engine computer and remove four nuts that hold the HVAC housing.
Inside you will have to remove the trim on the sides of the windshield, trim at the base of the doors, remove the trim below the steering column, remove the steering column, remove the trim on top of the transmission tunnel, remove the airbag computer, remove screws across the top of the dash and on the sides, unplug numerous connectors and remove the dash. You can just lay it on top of the seats.
The HVAC housing is then held in with two more nuts.
Once you get it out you then remove the screws that hold the Heater core in place. If you want to replace the evaporator coil while you are there ( a good idea ) you need to remove the screws that hold the top cover on.
You reverse all steps to install.
Do not forget to fill the antifreeze and warm the engine up before driving.
You will also need access to an ac vacuum/refill machine to recharge the ac.
WHAT YEAR IS IT? is it four wheel drive, two wheel drive?
To change the heater core on a 1999 Chevy 4-wheel drive, first remove the dashboard and drain the coolant. Unbolt the core from its mounts and remove the dash panel to be able to change the heater core.
The 2010 Dodge Challenger has rear wheel drive.
The 2009 Dodge Charger has rear wheel drive.
The 2006 Dodge Charger has rear wheel drive.
The 2004 Dodge Durango has rear wheel drive.
The 2011 Dodge Avenger has front wheel drive.
The 2014 Dodge Journey has front wheel drive.
The 2009 Dodge Avenger has front wheel drive.
The 2011 Dodge Charger has rear wheel drive.
The 2013 Dodge Dart has front wheel drive.
The 2002 Dodge Durango has rear wheel drive.