Here are directions to replace the heater core:
Disconnect the battery ground cable.
Remove the engine cover.
Remove the steering column-to-instrument panel bolts. Lower the column carefully.
Remove the upper and lower instrument panel attaching screws. Remove the radio support bracket screw.
Raise and support the right side of the instrument panel.
Remove the lower right instrument panel bracket.
Remove the vacuum actuator from the kick panel.
Disconnect the temperature cable and vacuum hoses at the case. Remove the heater distributor duct from over the engine hump.
Remove the two defroster duct-to-firewall attaching screws below the windshield.
Under the hood, disconnect and plug the heater hoses at the firewall.
Remove the three nuts and one screw (inside) holding the heater case to the firewall.
Remove the case from the van. Remove the gasket for access to the screws holding the case together. Remove the temperature cable support bracket. Remove the screws and separate the case. Remove the heater core.
Install the heater core.
Assemble the case and fasten the screws.
Install the temperature cable support bracket.
Position the gasket, then install the case in the van.
Fasten the three nuts and one screw (inside) holding the heater case to the firewall.
Connect and plug the heater hoses at the firewall.
Fasten the two defroster duct-to-firewall attaching screws below the windshield.
Install the heater distributor duct.
Connect the temperature cable and vacuum hoses at the case.
Install the vacuum actuator at the kick panel.
Install the lower right instrument panel bracket.
Fasten the radio support bracket screw.
Fasten the upper and lower instrument panel attaching screws.
Fasten the steering column-to-instrument panel bolts.
Install the engine cover.
Connect the battery ground cable.
Refill the cooling system as necessary.
you asked for directions- those are the directions. not sure what else you are looking for. What problem do you seem to be having with replacing the heater core? It is a straightforward repair procedure. IF there is a specific problem in this you are encountering, you have to give more specific information.
What have you removed so far? Have you got the right side of instrument panel raised and supported( I use a bungee cord to hold it up)? Have you removed the nuts and screw holding the case to the firewall?
I can describe them to you, but its a little confusing when you are standing right at the vehicle. Give me a couple of minutes and let me see if I can come up with a diagram to send you showing their location
Does yours have auxillary ac and heat, or just the front unit?
This is the only other diagram i have:
Two of the nuts are just above where the heater hoses go into the firewall. The 3rd nut is just below the hoses and to the right. You can unbolt the clamp holding the accumulator and it will move a little bit with AC hoses still attached to give a little more access.