I have a 1983 240D.

I have been experiencing problems with the speedometer and gauges, especailly the temp gauge. I am just about to the point of giving up and either taking them in to be fixed or replacing them with used. My question is am I better off getting what I have repaired or going for used parts? I know at least with the speedometer that I would have to reset the odometer, if I go used. Also, can I replace, just the temp gauge or do I have to replace the whole section with the fuel and oil pressure gauges?