2004 Chevy Impala coolant leaks inside

i suspect a leaking heater core or the 2 connections to it.

Disconnect the negative battery cable.
If equipped with a 3.1L engine, remove the air cleaner and duct assembly.
If equipped with a 3.8L engine, remove the fuel injector sight shield by performing the following procedures:
Clean the area around the oil filler cap/tube assembly location.
Rotate the oil filler cap/tube assembly counterclockwise from the valve cover.
Lift the fuel injector sight shield up at the front and slide it from the rear engine bracket.
Reinstall the oil filler cap/tube assembly in the valve cover.

CAUTION
Before draining the cooling system, allow the engine to cool to relieve the systems internal pressure and to avoid scalding coolant.

Drain the cooling system by performing the following procedure:
Raise and safely support the front of the vehicle.
Remove and clean the coolant recovery tank.
Place a 2 gallon pan under the radiator to catch the coolant.
At the bottom of the radiator, open the drain valve and drain the coolant to a level lower than the heater core.
Remove the radiator cap and open the air bleed screw (2-3 turns) located on top of the thermostat housing.
After sufficient coolant has been drained from the system, close the drain valve.

CAUTION
Engine coolant is a hazardous waste; it should be stored for reuse or submitted for recycling. NEVER dispose of it by dumping it into the environment.

Disconnect and plug the heater hoses at the heater core.
If equipped, remove the lower center console by removing or disconnecting the following:

Cigarette lighter Automatic transaxle shift handle Upper console trim plate from the front floor console by unsnapping it Electrical connectors from the upper console trim plate and remove the trim plate CD storage compartment from the front floor console by unsnapping it Raise the front floor console armrest and remove the compartment mat Console-to-chassis bolts and screws Electrical connectors from the console and remove the console from the vehicle

Remove the lower instrument panel lower compartment by removing or disconnecting the following:

Lower right instrument panel insulator Compartment-to-panel bolts and screws, from under the instrument panel compartment Instrument panel compartment door screws and the door Instrument panel compartment screws and plastic clips; then slide the compartment from the instrument panel Electrical connector from the compartment Ashtray and bracket, if necessary Lower heater duct Heater core cover and discard the cover seals Heater core mounting clip and bracket
Heater core

Hello my friend
you are two step away, you need to remove the heater core clip and bracket.
Try to remove the plastic frame without removing the passenger air bag.
Remove the mounting clip and bracket(plastic frame). Thing can be narrow sometime, but you are almost there.

If you can take picture of the whole thing, we will get it out.
It just require removing anything around it to get to the coor and remove it, that is all if you see that it will need to remove passenger air bag or other thing, make sure to desable them in right way. Label any parts, so the installation can be easier. It can be time consuming but at the end of the day, a good is what matter.
Send me picyure of the situation.

Thanks