The car originally had a km/hr speedometer, it was changed when grey marketing the car into the US.
If the clutch is not releasing correctly the problem very well could be hydraulics. Yes, it's just a clutch job, nothing special about it compared to any other clutch job. If you've never done an MB clutch before, about the only thing that you will find to be much different is the driveshaft. There is a big nut in the middle of the driveshaft that you must loosen in order to collapse the driveshaft an inch or so. After collapsing the driveshaft, you can then remove the flex coupling at the rear of the transmission.
If you are a good manual transmission driver, you should be able to run the transmission a half million miles or more with no trouble. I would recommend putting Mobil One in this transmission as a little insurance. If you ever DO have transmission trouble, rebuild parts will be a pain to find and quite expensive.