The evaporator lines can only be disconnected with the help of a spring-lock coupling tool, in the region of heater core housing. Replacing the heater core is not a simple process and requires that the instrument panel be pulled out and without much mechanical experience it is recommended it be done by a professional. Before proceeding, have the air conditioning system discharged by a dealer service department or an automotive air conditioning shop. Remove the black cable connection from the negative terminal of the battery. Drain the cooling system. In this operation replace the air conditioning accumulator. Remove the plastic fitting covers in the heater dick and evaporator core housing at the firewall in the engine compartment then slide open the plastic tabs on the heater hose fittings and use the spring-lock coupling tool to undone the evaporator lines. There should be plugging of all the open lines and fittings to avert contamination of the heating, cooling and the air conditioning systems. Lift the carpet and then unclasp the fasteners of the heater outlet duct and finally, take out this duct. Pop the instrument panel and take out the mounting nut for the fuse/relay box and shift it. Take out the evaporator/heater core housing mounting fasters and junction-box mounting bolt, and respectively, extend the housing away from the firewall and up and out from the passenger compartment after disconnecting electrical connectors and attachments. Undo the insulating panel seal at and around the heater core ad the inlet and outlets of the evaporator, then the temperature blend door actuator, and finally the heater core cover. Remove the heater core in the housing by lifting them straight off in this position. Remember, installation is the reverse of removal, if you reconnect the battery then refill the cooling system and have the air conditioning system recharged and leak tested by the shop that discharged it.