My service dog alerts me when I dissociate; because he does that trained alert, he counts as a service dog not an ESA. We did work with a trainer for a couple of years so that he would be obedient and mannerly in public, but the trainer mostly trained me Like seesaw, I was fortunate that my dog turned out to have the temperament suitable for a service dog.

In addition to his trained tasks, just having him around eases my anxiety. I do not have the degree of anxiety that you describe, but he does help some. It will attract a lot of attention- you will be asked by all sorts of people why you have a dog and you will be asked constantly if people can pet your dog. For me, having to say no to all the people who want to pet him is harder than saying why I have him. People are generally satisfied with my explanation of dissociation. But many people think that they should be allowed to "cuddle" my dog just because they love dogs. I hear over and over how hard it is for them to resist petting my dog. This despite his vest and his patch that reads "do not pet". Some people even argue with me about it. So that might be something to consider.

Trained SDs cost a lot of money, training one yourself will take a lot of time (and money for obedience school unless you have a lot of experience training dogs). Perhaps you might do well to start with an ESA, they are generally cheaper and require less training. Your school may well be willing to let an ESa attend classes with you. It would be worth asking.