Volvorally,

All too common. Age+pressure bearing+flimsy design = breakage.

Happiness, though; the instrument panel is easy enough to take off (see manual - may I recommend the Bentley?) and disconnect the various gauges. For fun and stress limitation, you'll want to tag the wires. Actually, I don't because there aren't that many, and I remembered where they all go. But I recommend tagging, 'cause it keeps things simple.

Once you have the panel off, you'll understand the design of the odometer trip reset button.

This will all go smoother if you start by going to the junkyard and pulling an instrument panel from a similar same car; this has two effects:

1) free training on someone else's car (hooray!)
2) You'll need a replacement for the broken part, and if you don't want to go to the dealer, the junkyard should supply several.

Best of luck,

Lanval