[instantkevin]

if the speedometer stops working, the odometer will stop working because the odometer calculates the distance based of what the speedo says. it depends on the speedo.

i dont know why your tach would stop working. it gets its reading from a single wire connection to the distributor. (i think its a yellow wire).

the speed sensor is located at the rear, driver side of the transmission (most of the time), right ahead of the driveshaft. it will probably have a wire coming from it and one bolt holding it in. it's very easy to remove and not an expensive part. (when u remove it, if the plastic gear looks fine, the sensor is probably fine).

sounds like a problem with the gauges to me. maybe get another gauge panel of eBay, try it and see what happens.