Volvo Repair: volvo speedometer, signal instrument, ebay

Question
The speedometer/odometer/cruise on my 91 740 non-turbo has quit working.    
All other gauges OK including the tachometer, which is use as a speedometer
proxy.  The first owner of the car had the speedometer head replaced at 48K
miles.  Is this a weak spot in the engineering?  What should replacement part %
2B
labor cost?   Can I do it myself?

Answer
Make sure you are getting a signal from the speed sensor, located on the differential. the wires tend to break there, sometimes the insulation of the wire will still be intact and the wire inside is broken. It is an AC v signal.Instrument cluster is not difficult to remove, should be a couple screw going up in the cluster or two screws from the front, depending on which style cluster you have.You would probably pay at least an hour of labor, new speedo heads last I checked were about 600 bucks. Good used ones are available from junk yards or even ebay.