I just finished that task on my own 94 850 Turbo. Not too difficult, but care is required. You have to basicly tear down the instrument cluster to get at the odometer and replace the little gear. Just a lot of torx screws and then carefully separate the gauges from the mother board. Also, a note about the Bay 13 instructions on removing the cluster from the dash. It's quite detailed and almost perfect instructions, except that there are three green electrical connections that must be disconnected. Two on the top (as mentioned on Bay 13) and a third on the back of the cluster that is tougher to get at. Just don't pull it out thinking that the cluster is free when there is a third connection in the back.