Is this something I do from inside the car or from outside in the engine compartment? I thought it was from outside so i started taking the little nuts off and trying to pull of the cover, then i saw somewhere where the core comes out from the inside.

Im confused.

 

you are correct on both your statements.
google this :
[PDF]1st Gen Heater core repl - Worldwide Camaro Club Forums
www.worldwidecamaroclub.com/pdf/tech/heatcorerepl.pdf

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decided it was time to tackle a heater core replacement to add more enjoyment to ... we replace the heater core in an A/C equipped '69 Camaro. These steps.