How to Removal and Replace Heater Core

You need a copy of the manufacturer's service manual for a huge job like this. You won't find this in a Chiltons or Haynes manual. Those only cover things competent do-it-yourselfers can do. There are many pages of instructions, and it will include using a refrigerant recovery machine to safely discharge the AC system.

You can also buy an online subscription for just your car. The two that almost all independent repair shops subscribe to are AllData and Mitchell-On-Demand. Those include everything found in the manufacturer's manuals, plus recall and service bulletin information and diagnostic information.