Service dog

My fiance and I were talking tonight about looking into getting a service dog for our son who has autism. He tends to have meltdowns/anxiety when in public places. Going to a restaurant, a museum, the doctors office, anywhere besides walmart is a horror show. I've done a few quick Google searches and saw that a service dog could help calm and keep him calm and ease his anxiety in social situations like this. I also saw that a trained service dog could be upwards of 10,000 dollars.

Has anyone here ever had a service dog and could give me some information on it such as the process of it, how much your service animal cost?