If you have any reason to believe that the ignition components are original, you should certainly replace them first before launching into more expensive repairs/replacements (fuel distributor, for example). Your indy should have at least checked their condition (are the plugs sooty? is there arcing from the wires? etc.). When you replace the plugs, the conventional wisdom is that you should only use copper core non-resistor plugs.

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1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't