They always tell you to do this for a reason. In this case, we're going to remove the ECU, so it's best to prevent any issues by disconnecting the battery terminals before you start.

Put a pan under the front driver's side of the truck. Get a large one, the coolant splashes all over the place cause it drains out onto the frame rail instead of strait down.

Unscrew the plastic wingnut/petcock on the bottom of the driver's side of the radiator. It's real easy to get to if you already have the fender wells out, but you can reach it from the top if you undo the nut on the airbox, and move it out of the way.

When the system is fully drained, tighten up the petcock, and replace the airbox.

Remove the coolant overflow tank on the passenger side of the engine bay (3 - 10mm bolts). This is not a necessary step, but it allows better access to the hoses your going to fight with in a minute.

Use a large pair of pliers move the clamp bands that hold the heater hoses to the heater core a few inches down the hose.

Using that pair of pliers, clamp down the ends of the heater core's copper pipes that are inside the hose. Bend the hell out of them, just squeeze, till they are obviously no longer round. (be careful with that formed hose, its not cheap to replace). This will make yanking the hose off about 100x easier.

Pull the hoses off the heater core

Remove the Heater core's tube support ( 1 - 7mm hex screw). Its the little piece of metal in the shape of a "W" that attempts to prevent heater core breakage.

Remove light bulb from passenger side footwell, or disengage by removing it's fuse. This light gets hot, and will burn your arm quite nicely (my second syclone related injury).

Remove passenger side footwell trim panel (7 - 9/32 hex screws). Its that dark plastic piece just under the dash.

Remove passenger side kick panel (4 - phillips head screws).

Remove ECM (1 - 9/32 hex screw). Remove the screw, and carefully pull it out from under the dash.

Unplug and Remove the ECM. You'll need to unplug it from the harnesses, and place it somewhere safe.

Remove Ash tray

Remove Radio Trim panel (3 - phillips head screws) The cigarette lighter simply comes off by spreading the two plastic arms away from the shaft on the back side of the trim plate.

Remove Radio. (2 Hex bolts) Remove the bolt on the far right and left brackets, then pull the stereo out, unhook the wire harnesses and antenna wire.

Remove access panel in the rear of the glovebox (2 - phillips head screws)

Remove bolt on passenger side of truck that holds onto the dash (1 - 10mm Hex bolt). Pictured in step #4

Carefully pull out on the bottom of the dash, moving it out, and down to hook it on the tab that it was screwed into. This is to aid in removing the Heater core cover that needs a little room to move.

Removing the screws (6 - 7mm hex screws) Four are easy to get to from under the dash (2 on bottom, 2 on right side).

The top screws are accesible through the radio opening, and one in the glove box opening. These are the real pain of the group. Have fun, don't loose the screws ;)

Disconnect the Heater Vent Hoses that are connected to the top of the cover.

Cut the tape. There is some sticky foam stripping in the joint between the rest of the ducting and the cover, Cut it at the bottom(under the dash), and at the top (from the radio cavity).

Begin Yanking! Pull on the heater core cover from the bottom right side. (towards rear of the truck). Then try to move the cover to the right to disengage it from the ducting on the left side.

Rotate the cover so the bottom goes toward the front of the truck, and the top, towards the rear. This is to get it around the heater core that rests inside. You'll have to pull the "T" shaped ducting (look through glove box) out of the top of the cover to get it out. Be careful, its plastic. It will come out, just be nice, and wiggle till you manage to get that SOB out.

Remove the hold down straps ( 3 - 1/4" hex screws). There are 2 metal straps holding the Heater Core in place, Remove the left one (both bottom and top screws). The right one doesn't have to be removed completely (its almost impossible to do). Just unscrew the bottom of the right strap, and bend it up.

Now, remove the Heater Core. Pull, and rotate until you can manage to get it out. It's most likely full of coolant, so be careful here. You could put the tube covers off your new heater core onto the old one to prevent spillage (if you're new one has them, that is).