I have a 1992 Buick Riviera 3800 engine. Where is the heater core located exactly?

If you look under the hood of the car, look on the passenger side firewall. There you will see 2 hoses (one right above the other) going into the firewall. That's where the heater core is. The way to access is to remove the passenger side kick panels, then the vent control box thingy, and the computer.