[M24]How do I get a diagnosis?

So, I recently discovered I probably have Asperger's. Which explains a lot why I can't pass job interviews. I always thought I just had social anxiety and was introverted, but Asperger's explains a lot about me.

However, I do have some questions, though not the usual kind.

How do I get a diagnosis?

Do I go to a hospital/doctor or a Psychologist?

Who's qualified to give the diagnosis?

How much does getting diagnosed cost?

If it does cost money, I'm unemployed, so money is tight, AND I have no health insurance. How can I make it cost less?

How do I prove I have it to an employer so they'll give me an asperger's-friendly interview?

Do I get a certificate of asperginess or would I have to refer everyone to the person who diagnosed me?