It is a somewhat big job. Here are the directions I was able to find for you:
Disconnect the negative battery cable and properly drain the engine cooling system to a level below the heater core.
Disconnect the heater hoses from the core tubes near the cowl.
The instrument panel carrier is designed not only to provide access to parts through removal of the carrier components, but the carrier will also tilt downward as a complete assembly to allow access from the top. If this is desired, remove the retainer screws along the top and bottom of the carrier assembly (refer to the figure). The instrument panel will then tilt as an assembly into the cab. It is necessary to unbolt and lower the steering column from the carrier to allow for maximum movement of the instrument panel.
The instrument panel must be removed or repositioned for access to the heater core case. Unbolt and either tilt the instrument panel forward or disengage the instrument panel components and remove the panel from the vehicle. In most cases, tilting the panel forward should be sufficient for the necessary access, but if necessary remove the panel refer to Body & Trim in this guide.
Unfasten the heater core rear case retaining screws, then remove the rear case for access to the heater core.
Loosen the retainers and remove the heater core retaining straps.
Remove the heater core and seals.
Install the heater core and seals, taking care not to damage the core tubes when inserting them through the cowl.
Install and secure the core retaining straps.
Install the rear case and secure using the screws.
Reposition and secure the instrument panel and components. Tighten the cowl screws to 17 inch lbs. (1.9 Nm) and the lower instrument panel screws to 66 inch lbs. (7.5 Nm).
Connect the heater hoses to the core tubes.
Connect the negative battery cable, then properly refill the engine cooling system.
Run the engine at normal operating temperature, then check for leaks.
Tuesday, November 23rd, 2010 AT 11:48 PM