[valiant67]

Welcome.
I think you will find that the 1990 unit won't work with the 1992 car and that you need to find a 1992 or 1993 to get parts from due to changes in the communication protocol used in the different years.

 

[valiant67]

The other alternative is to replace the failed gear in the mechanical cluster. There have been a few posts about this, though probably for other models the idea is the same. here's one:
http://www.allpar.com/forums/topic/147785-odometer-repair/