The lower dash has to be disassembled, not the entire dash. The a/c system must be discharged because the evaporator is in the same box as the heater core and the box must be removed. For $80.00, it is highly advisable to replace the evaporator while doing the heater core. I bought a retrofit kit and recharged the system myself. I understand it's better to have it done professionally, but money was an issue for me. My air is ice cold with no leaks. Make sure to replace the dryer. I also replaced the H-block for $30.00. It's simple to retrofit. It's not hard to do, just time consuming.