Three of domain names stolen...

[Dr Bizzaro]

Someone tried to do that to me at Network Solutions about 5 years ago. (And a bunch of other sites as well at the same time.)

They only got as far as changing the contacts. When I saw the changes go through I contacted NetSol ASAP and after 3 days and about 15 hours on the phone, I got it all straight. The DNS never got switched, so I never fully lost control of the website.
It pissed me off to no end and it was a long 3 days of bullshit.

Network Solutions changed their security since then and I've had no problems.

I've heard nothing but bad things from GoDaddy as well. I have no domains there.

Be careful about threatening a lawsuit. I have read in other threads that some registrars phone people are told to hang up on people if a lawsuit is mentioned.
I would have a lawyer call them directly.