History's full of situations where you're almost certainly being ripped off -- like buying an exorbitant Church indulgence to absolve you of coveting everybody's wife. Protect against the modern era's biggest rip, with Repair Pal.
Pal's a website that deduces fair price on repairs for over 400 different rides, by analyzing data points on thousands of prior invoices (because if it's invoiced, it must be true). Hit the "estimate" page and enter your make, model, year, zip code, and "service type", then select from dozens of options, from an oil change to exhaust manifold gasket replacements; you'll get back a range of costs, adjusted for your locale and broken down into parts and labors -- hey, your overuse of the clutch doesn't ridicule itself. When it's time to pull the trigger, RP's got an index of nearby repair shops, all ranked by users, who give high marks for good work, and low marks for inferior waiting-room coffee.
Soon, RP will cover scheduled maintenance, but don't hold your breath for bodywork -- because what may look like a scratch to you, to a devout car-dinal will look like The Apocalypse.