First take off the lower dash paneling (the one with the courtesy lights) on both the driver and passenger sides.

Next take off the section of paneling right above that on the drivers side and disconnect the trunk release (quick disconnect) I believe this section of paneling has one or two screws in it.

Next take off both fuse panels on the driver and passenger sides

Next tilt your steering column down and open your glove box. There is a screw for the main dash panel (that covers the radio, HVAC, instrument cluster) on that side that the glovebox covers and another screw under the drivers side fuse panel. Take both of those out and use a little force and pull the whole cover off. The ring around the ignition key cylinder will pop out immediately. Just disconnect the hazard button (quick disconnect)

Next engage the vehicles emergency brake and turn the key on and put the vehicle in neutral. Then take a small flat-tipped screwdriver and pry out the rubbery-plastic ring around the shifter. Comes out easy.

Next remove the rubber insert that is on the center console (directly below the radio and HVAC panel) Remove that screw.

The whole upper part of the center console should now come apart with a little force. Now pop out both of your heated seat buttons (If so equipped) and disconnect the wiring harness that connects the front and rear cigarette lighters and the traction control. You should now have the whole upper part of the console free and just turn the whole unit side ways to get it out and over the shifter.

Next open the lid to your center console and take out the rubber insert at the bottom. Underneath you will find 6 bolts. Remove ONLY the two larger ones (10mm head, if I remember correctly) Now remove the two bolt (10mm head, if I remember correctly) that are in front of the shifter. The whole unit should now be free and just repeat the same steps for the upper console for removal.

Next cut your carpet from the firewall to the shifter. Make sure you cut in the center, so the center console covers up the cut. Peel back both parts of the carpet on the drivers side, and passenger side.

Now make a v-cut on both ends of the heating duct (that delivers air to the rear passengers underneath both seats)

NOW FOR THE FUN PART!.... (SARCASM)

Drill out all the plastic rivets that hold on the heater core cover.. (I used a step-bit) I HIGHLY recommend using a 90 degree drill, because there is very little clearance for most of these rivets, and they are all a huge pain to get to. You will see a small hole looking thing next to each rivet. You don't need to drill those. Those are there just for the plastic injection molding process I believe. Once you get this off, take it to the bench and use a hacksaw to cut the two main tabs off (bottom side) This will make installation MUCH easier. And they are not used anymore anyways.

Now take out the four 5.5mm bolts that hold on the main cover for the heater core. There are more plastic rivets to drill out. Once you get all them off, the cover should be removed easily, and you will now see the heater core

Next pop the hood and take off the clamps off both of the rubber hoses that hold on the heater core. There are a huge pain to get to. A pair of Channel Locks with short handles works the best. You should now be able to pull the heater core free from the firewall.

Now set the old heater core next to the new one and align the new metal tubes the same way as the old one. This will make life much easier.

Next install the new heater core. once both metal tubes are through the firewall, have a friend hold the new heater core in place while you put on the rubber hoses and clamps on the engine side.

Now bolt up the main plastic cover for the heater core using just those 4 bolts. Nothing else is needed to replace those plastic rivets, those 4 bolts are plenty.

Next slide the bottom cover into the ducting that you made the two v-notches in. Have some small self-tapping half inch long screws ready and screw the lower cover on. (I only used 2 self tapping screws. One on each side. I pulled on it real hard and it didn't budge. 2 screws is plenty.

I used zip-ties to sew my carpet back together, so it wouldn't spread apart any further. (see photo)

The rest of installation is just the reverse of disassembly. Just use your brain.

I typed this up from memory. I did this two days ago on my '04 monte, so I don't think I left anything out. If anyone can correct me on anything, feel free to chime in. This may only work on the 6th gen montes. I used a Delphi heater core Part # HC10004. Made in USA.

 

I'm fairly new to using forums, and I'm not sure how to attach photos. If someone could help me out here, that'd be awesome.