Well, I haven't filed such a claim and I'm not a lawyer but I had a career in administrative law, so I know a little about how legal claims work.
This is a legal process that involves the application of statutes (written laws), case law (legal precedents established in prior, similar cases), and administrative procedures. It's complicated and full of pitfalls for the unwary. That's why there's a legal profession, so get a lawyer.
If you have a good case, and it sounds like you do, a lawyer will take the case on contingency, meaning that they take a portion of what you win as their fee. If you don't win, you owe them nothing. If you feel confident that you have an ironclad case and can't lose, you can hire a lawyer on an hourly basis, paying a rate for the time they spend on your case. If you pay that way, your fee will probably be significantly less than you'd pay on contingency if you won, but you'd have to pay regardless of the outcome.
We have so many lawyers these days, chances are that you already know one who either handles this type of case or can recommend one who does. If you don't know any lawyers, chances are that some friend or relative does. If not, you could call your local bar association to find one who does this kind of work, or just go downtown and find a law firm.
Good luck!