Maybe a good solution is to let the shop recheck the bike (a loss of time on their part). Then, instead of taking money OUT of the drawer, ask for a coupon for your next tune up to be free. Mistakes happen, but it's not always necessary to run away from that shop never to return. Let them fix their mistake, keep the money, and offer you something tangible in return. Cool out, they might be a bunch of great guys that can appreciate your concerns and your willingness to let them make it right, while retaining you as a customer.

Or you can learn to work on your own bike. Then you have no one to blame but yourself.