Fixing the heater core:

disconnect the battery....and wait atleast 3 mins for airbags to discharge..............

first take off the glove box and you will see this.

once the glove box is out disconnect the evap from inside the engine conpartment. discharge the a/c into empty tank. then take out the screw in middle of the evaps metal lines and pulling them out.

once these are dissconnected go back under the glove box and disconnect the screws to release the evap box. also in the process disconnect all the connectors to the wiring harnesses

once the box is out you can see the heater core

the heater core is in the back of the box, the white piece sticking from behind is the heater core strap this just pops out with a flat head.

unscrew the four screws on the 2 hose connectors connecting to the heater core

 loosen the two hose clamps on the firewall inside the engine conpartment.  exposing the yellow plastic hose connectors

 pull out the connectors from under the glove box and pull out the heater core.

replace the heater core and put everything back together