I went through something similar this past summer. My truck was to be done by April 25th, and July 15th I showed up with a trailer to get it. He tried to say I couldn't remove the truck until he was paid for supplies. I called the local Sheriff, and after showing proof of ownership, I was allowed to get my truck back.
As far as suing him. Get all your items back first. Don't allow him to do anymore work. Nothing worse than having a pissed off body man work on your stuff
Get a lawyer that handles business law. Talk to some people and find one that will do the case contingent of getting a settlement... be prepared to give him 1/3 of final settlement plus his actual costs. The shop could also have an unexpected fire, but that would be illegal
