1 Answer

First remove all the water from your system by draining the radiator, it's best to do it this way so you can add new coolant and keep the mess to a minimum, after your water is drained, go ahead and remove the heater core feed lines.
Remove top of dash pad, do this by removing several screws located under the foward lip of the pad, don't forget the screws in the defroster vent holes!
Remove the lower trim panel from the underside passenger side dash ( if there is one there)
Look under the dash on the passenger side and you will see the plastic box in which houses the heater core, remove all the screws that surround this box, there will be one screw on the top that will be very difficult to get at, this is why you have removed the top of the dash so you can get at it with two hands,if you need to see this screw get outside of the car and look down at the dash from the passenger side and then your going to have to depend on feeling with your hands.
At this point you should have the plastic box off and now your looking directly at the heater core, the core is held in place by a steel clamp fastened with screws, remove these screws, and remove the clamp.
Now it's time to remove the heater core , get some plastic sheeting and lay it around the passenger foot well because there going to be some water in the core yet, pull it out gently, you might have to wiggle and gently pull, take your time, it should come out fairly easy.
Once you have the old core out, it's time to install the new one, I can't tell you how important it is at this point to be very patient when installing the new core, you may have to slightly bend the new core tubes to get them through the firewall, you may end up taking it out a couple of times BE CAREFULL!!!!!!
Once you have sucessfully got the core in place, install the core clamp, then re-assemble

Make sure that after you have installed everything and you fill your system with water, slide your heat temp control to full heat the check everything for leaks!  http://www.thirdgen.org/heatercore