The only two items that sound plausibly expensive to me are the faded paint and the fluctuating idle.

I suspect the clear coat is shot, and no amount of buffing is going to bring it back.

The idle problem could be something as cheap as a vacuum leak or as expensive as a throttle actuator.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".