My 2 cents:

First thing to do, Penguin, is to back off of him. He knows what he did; you know what he did. When you talk to him next, your best tact is to ask him how he's going to fix this problem.

Going berserk on him will end badly. He'll fall back on calling you a liar, at best, trying to save face with his buds; or, at worst, he'll shoot you.

We don't want a dead Penguin.

Most people fear a quiet determination, as opposed to someone that just wants to jump in their face.

Let the people who will communicate with him know you've been burned. That you will never let it go. That you are considering your many options, but willing to let him make things right.

Here's a thought: if you've been ripped off, then what's done is done. Play it right and you have nothing more to lose. But very bad things are in store for him. Not today, but some time of YOUR choosing. And even when he makes it right, you'll still have the option of a brick tossed through his windshield.

Don't let it eat at you. Draw up some 'perfect plan' ideas when you have free time. You lost $850? Make him lose $1700.

Most important: don't get caught. Fuck with him in very safe ways. Ways that leave him unsure of who did it---maybe just some random events.

Good luck, Penguin. Before acting, run it past a trusted friend.