Changing heater core on 1985 Camaro?

Has anyone ever changed a heater core on a 1985 Z28 Camaro. I called 5 places and they all say it will take over 7 hours to change it and they want $565 and up.They said they have to take the whole dash out. I know you have to drain coolant and take the two hoses off and that the core is behind the dash just don%26#039;t know the best way to get to it.. Auto zone site says you have to remove the lower right instrument panel to access the heater core box. One other site said to take the top dash pad off to get to it. I thank you for any help you can give.|||you have to remove the whole dash b/c its behind the dash.