Does the speedo just pull out or do you have to remove the panel it is set in ?
There must be a connection for odometer reset and speedo cable and panel bulb ?
Does not appear to be a way to get at these from behind the panel

there's a tiny screw on the odometer reset knob and a thin nut that holds the cable in under the dash.

Gauge just pops out of the panel - no need to unscrew. I found it easiest to unplug the reset cable on the speedo side rather than the knob side. Just pulls out.