Name change process

Does anyone know how it is in California ? I'm not talking about for my kids i'm talking for myself , I grew up hating my name I go by my middle name and I remember doing research when I was 19 but didn't have the money to do it , I believe it was $500 in California(correct me if i'm wrong). When I told my parents about it they told me " you can just go by your middle name for the rest of your life" yeah ok, but what I don't like is when I have to do paperwork or go to the doctor etc I always have to put my real name and the nurses always call out my real name and I don't like it. What I want to do is change my middle name to be my first name and want to add a different middle name also , I'm married but haven't changed my last name to my husband's but I will. So anyways, does anyone know how much it costs ? And do I have to go to court ?