Where is the heater core located for 1992 Sunbird 2.0 LE located ?.

There is no easy way to replace the heater core, which is under the dashboard. Heater core replacement is a long, tedious process. That's why garages get big bucks to do it. But you can find plenty of schematics and guides on the process on line, or purchase a repair manual (always a good idea when you own a car over 10 years old).