To service the Digital Cluster, you'll need these supplies:
7/32" Nut Driver
Optional, but really good insurance: Static control wrist strap (radio shack again)
Disassembling the Digital Cluster
IMPORTANT: Wear the properly grounded static wrist strap the entire time the Digital Cluster is apart! These were built in the mid-80's, and as a result, contain CMOS semiconductor components that are extremely sensitive to static electricity.
Place the Digital Cluster face down on a soft surface and remove the five 7/32" hex screws holding the metal panel to the rear of the panel (shown in red in figure 2). If there's an additional sideways connector (shown in blue in Figure 2), remove this screw and set it aside. It's shorter than all the rest of the screws, so make sure it gets put back in the proper location when you reassemble the cluster. Remove the metal cover and set it aside.
Remove the seven 7/32" screws holding the top circuit board to the Digital Cluster case. These are shown in Red in figure 3.
Disconnect the odometer wire and carefully lift the top circuit board out of the housing.