Based on my own experience ('87 3.5efi) failure of the odometer is a prelude to the speedo itself developing a very 'wavy' needle, which will result in MOT failure when the time comes. I've attempted to have mine repaired but the specialist was...
My cd player keeps playing up, says no disc when there is, stripped it down twice in my 3 years of ownership and it works again even though I can see nowt wrong through my untrained eye and I haven't adjusted anything. Got a good , apparently...
I seem to remember that, despite the allegedly high standards of police vehicle maintenance, these cars were usually on their third engine by the time they were cast out of service.