How do you find out what your health insurance does and doesn't cover?

I want to go to a dermatologist but I don't know if it is covered by my health insurance and I don't know whether I should be asking the doctor or the health ins. company. Who would I ask (in any case, not just the dermatologist, for example if I wanted to go to a regular doctor)? Is having health insurance difficult to deal with? I've never used it before, always just paid cash. Thanks in advance!
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health-quotes.talk4fun.net - here is my health insurance plan. As I remember they can provide such a service.
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