What do I look for in a used C32? What are the added costs besides MPG, Insurance and the potential tickets? What should have been done to it at 100k miles?

Price range for a 2003 with 100k?

Thanks

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03 SLK320
98 E300TD 320k Miles
75 914
02 Suburban

You should ask this in the c32 section on one of the other forums were you have a better audience. Basically service wise it should follow the factory scheduled service or better.
Outside of that. Stepper motors or hvac, front suspensions components, bushings, joints etc.
Bottom line have it inspected by someone that knows.