I always cleaned my caps (my current car doesn't have one...) I would just scrape the gunk off the elctrodes. When the car would hesitate on accelleration I would know it was time to clean the cap. The rotor can be a different story if it has a special material on the end. Anyway, if you just scrape the crud off then you shouldn't affect the gap.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra