Well I took the plunge and decided to do this myself. I got eveything apart and installed the heater core but can not get it realigned to fit all of the screw holes to reseat the box. In the attached picture when get the one nut on the right in the whole the others do not allign. The wholes will not reach to the left far enough. I think I will have to take the entire dash out.
http://i235.photobucket.com/albums/e...h_98df58d2.jpg
Now if I have to do this I can't get the wiring harness off to move the dash. I have loosened the middle screw but it won't come out all the way and the harness will not disconnect. Any ideas?
http://i235.photobucket.com/albums/e...h_dba712ba.jpg
Hole not whole

Noone has any ideas how to take this harness apart ?

You gotta take the blue tabs out of each side. They are almost like forks.

Thats how you take the harness off. Use a screw driver. Hope that helped

It'll come apart, you just need pull back on the blue retainers and work the connector loose as stated above. Patience is key.

Speaking of patience, please review the rules of the forum, paying particular attention to rule #4. Thanks.

Thank you for the help will look at it tonight and I apologize for breaking the rules.

On my 98 Blazer there was a screw in the middle of the plastic block that all of the wires are mounted in. There is a plastic collar that sort of hides it but you've got to back the screw out before you can pull the two blocks apart.

I ended up taking the dash completely out. It gives you much better access to everything and you can stain/paint the dash if it is faded or discolored. There are TWO plugs that need disconnecting, though. The large plug that you are wrestling with now and a smaller one above the emergency brake release handle. You'll also need to disconnect the emergency brake release cable and a couple of other minor electrical connectors.

Also, there are 4 "L" shaped brackets and a large "U" shaped metal brace under the steering column that comes out. Then remove the two nuts that hold the steering column in place and lower it.

Be careful when moving the dash as the vinyl covering becomes brittle after a few years of exposure to the sun. Get a helper.

Do yourself another favor and throw those two bastard bottom screws in the garbage. I replaced them with a regular 10mm machine threaded bolt about 1 1/2 inches long.

I just did this Blazer heater core job over the Thanksgiving long weekend (and then some) so it is still fresh in my mind if you need suggestons or help