It should be relatively easy to remove the dash cluster from that Concord. There are about 5 or 6 screws that run along the upper edge of the dash cluster, a couple of screws just inside the glove box door, and a screw on the side between the wiper and headlight switch. You will have to snake your hand up behind the cluster and unscrew the speedo cable, then the whole cluster assembly should just tilt forward at the top and lift up out of the dash. Unplug the wiring and you're free!
What might be screwing you up is the fact that the overlay for the cluster includes that piece that surrounds the center AC vents and that all of it must be removed as a unit. However, it's not too bad a deal. I've taken enough of those dashboards apart I can pretty much do it blindfolded.
The speedo cable is what's keeping the dash cluster from pulling out enough to do anything.
I have really long skinny arms and know the particular yoga pretzel position to get into (laying on drivers seat on my back, feet in the air, right shoulder on the hump) and know the path through the under-dash junk to reach the knurled nut that holds the speedo cable in. I scrape my arm on the shelf support and the heater switch or something up there, but it beats dash disassembly.
If you remove the radio/heat-AC center piece, and extract the AC duct at the top (if no AC there's just a blank plate, even easier) you can reach your right arm in easily. You can even see it!
Put a towel over the steering column first, else the dash cluster will scrape the hell out of it.
With the speedo cable off, you should be able to extract the dash cluster enough to do stuff. In the way is the light switch, you have to sort of work it 'around the corner' of the dash on the left side.
When I wired my Hornet, I made the cable bundle nearly TWO FEET so I can take the !#$%!! thing into my lap sitting in the seat. Still have to do the gymnastics to put that nut on/off though.
Maybe if you got a longer speedo cable housing, you could get it to pull forward enough to do this without climbing underneath.