1994 Chevrolet Camaro heater core replacement

That is a huge job on any car. You didn't include any details to help provide a better answer. Do you have air conditioning? If so, you'll need expensive equipment to recover the refrigerant and recharge the system. Is the heater core leaking or plugged? You didn't list any symptoms. Your best bet is to get a copy of the manufacturer's service manual and read through the pages of instructions and drawings to see if you still want to tackle this yourself. Expect to spend a weekend doing this repair and take a lot of pictures as you do it.