Well he is coming to a message board asking questions about his contract and a potential criminal act. An Attorney can review his policy for him per state law and advise him on the potential criminal element and or the garage owners liability.
The OPs carrier is addressing his loss. So it's only a question of the value. I can tell you... 9 out of 10 plaintiff attorneys don't have a clue about vehicle values. Nor should/would they... as their is no money to be made from it. The attorney would need to charge the OP an hourly rate. Despite what they tell you on TV, attorneys don't work for free.
As far as liability... I'm pretty sure if a 3rd party takes your vehicle and does not return it that they are liable for the loss. It then comes down to coverage. An attorney can't do anything about a denial of coverage to a 3rd party.