I've got a couple of problems with the instrument cluster - burned out indicator bulbs, backlighting bulbs, and the odometer doesn't turn when I drive down the road.
There are 6 Phillips screws around the perimeter of the cluster. It will slide out, but will be held by the odometer cable, the trip reset cable and a mess of wires. To release the trip reset cable, get under the dashboard and find the knob. The knob is held onto its shaft by a tiny setscrew. Loosen the setscrew and slide off the knob. The nut holding the shaft has two tiny vertical slots. You may have a better idea or a specialized tool, but I put the blade of a small flat-blade screwdriver in the slot and gently tapped it. It came loose and I took off the nut and the cable is now loose.
Now on to the wires. In a more modern car, there would be a giant connector that would disconnect all of the wires from the instruments in one shot. In 1973, not so much. Some of the wires are connected to the instruments with push-on spade connectors. Some of the wires do go to a normal connector. Several other wires are hardwired into the wiring loom and go right into the back of the gauges. Let's examine the three instruments in turn. I've read other blogs that say to take pictures of the wires so you can get it back together later. I took pictures and drew each wire's color and position.
Left-side instrument: Brake light, oil light, gas gauge. This multi-function instrument has a bunch of wires and luckily they're easy to handle with spade connectors and sliding out the small bulb holders.