[Oldsguy]

You need small hands! Actually, almost anyone can do it but it is a tight job. Most of the fastners are on the firewall, some are small bolts and some are nuts. Don't ask me why they do it that way but they did, probably for alignment. Anyway look at the firewall on the passenger side and notice a pattern of bolt head/nuts in a rectangular pattern, maybe eight on top a couple on each side, and eight on the bottom or at least something near there. There are a lot. They hold in the core housing which is on the inside of the firewall in the passenger compartment. You will have to remove all of those fasteners, some are a tight fit closest to the wheel well. You will also have to remove some stuff in the passenger compartment, probably the glove box and some air door controls ventilation hoses. Depending on the kind of ventilation system your car had they may be solid cables or vaccum hoses, hope for the hoses as they are easier. Label everything and take pictures or draw sketches. Once all the fasteners are loose you can remove the air box (plenum) from the inside and then the heater core comes out (from the inside), of course remove the supply and return hoses for the coolant too. Well that's about it.