It is in the firewall under all of the a/c ducts. Big job. Get a manual on your car to do the job properly.
Detach the screw that attaches the heater duct on a Chevy Cavalier and remove the heater core. Once this is done you can replace the faulty heater core with a functional one.
copy link and paste... http://www.v6z24.com/howto/heatercore
diagram for a 92 Chevy van g20 Heater core
replace heater core in a 1991 Chevy work truck 1500
its leaking under the car around where the dash is
No it will not
Looks like a piece of cake. Check out the following link: http://www.automotiveforums.com/vbulletin/t490722.html Its a how-to with pictures.
Bad heater core.
heater core leaks
Either the linkage from the temp control unit to the valve on the heater core (which is behind the radio and temp controls) or it is the heater core itself.
$52- $208 roughly. depends on if the heater core is bad.
You do not need to completely remove the dashboard in order to change the heater core. Remove the water hoses from the heater core. Remove the heater core retaining bolts. Reverse the process to install the new heater core.