There are several possibilities on the high rev. First there is the idle control knob on the dash just under the instruments. It might be set way too high, and/or the linkage may be way out of adjustment.

On the hard to start, could be valves not adjusted properly, glow plugs not all working, compression low, old bad fuel.

Would be best to search on "hard to start" in the archives for that problem.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150