The basic audio plugs will be available at any stereo store.
The more specialized stuff you are likely out of luck unless Kenwood can provide them directly
Spark plugs and wires
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No, some parts do not work well if oiled, e.g. spark plugs in a petrol engine.
New spark plugs and possibly plug wires.
generally just spark plugs and pcv valve depending on environmental conditions other parts may be in need of replacement.
Fuel filter.. Air Filter.. Spark Plugs...
Different engine call for different plugs. You need to BClear as to what you have. Look under the hood for a white sticker, It will identify you engine size as well as the gap for the plugs. Or call a parts store.
Any platinum plug. You will need to gap them properly, or buy plugs specifically gapped for the particular engine. You auto parts store can help.
just ask them at the parts store, they will be able to tell you what plug you need.
To replace spark plugs, you can use a socket wrench, but a socket made for removing and replacing spark plugs is needed. This socket is relatively inexpensive and can be found at most auto parts stores.
a short repair harness is available for most alternator connections from any good parts supplier