Mechanics vs Medical Workers

I often compare mechanics and the laws which restrain them and the laws which are supposed to restrain medical workers which DON'T in any way stop them.  Here is an example from my own life...

My "economy car" a 2005 Mustang has 140,000 miles on it.  Quite naturally it is beginning to need repairs.  My engine light has been periodically coming on, so I have taken it to a mechanic several times to correct the problem.  Unfortunately it hasn't been corrected in full as the light keeps coming back.  So I stopped by the parts store yesterday which advertises "free" diagnostics for the engine light problems.  You know why they do this...they hope you will purchase repair items from them, which is exactly what I did.  A forty dollar part was in order.  One of the fuel efficiency probes on my catalytic converter was burned out, causing the engine light to come on and forcing the fuel injection system to try to correct a perceived error in the gas/air mixture.  That made my car idle roughly.

The problem as been corrected for 40 bucks and a little of my time rolling around under my car.  My mechanic probably would have charged me 200 dollars for the same repair.  Too bad medical care wasn't as simple as this!  There are no "parts" stores where we can have a free diagnostic test.  We can't just fix it ourselves and avoid medical treatment, like we can generally avoid mechanics. 

With mechanics, we will always get an "estimate" of the cost of repairs.  We can shop around.  We can find a "good" mechanic.  Apparently we are not entitled to the same with regards to medical problems.  Just try to get an estimate from your medical people...  There is a wall of silence around their particular skill level.  You cannot stop them from doing things to you that you did NOT give permission for, like you can with mechanics.  It's odd because medical care is exactly equivalent to mechanical care.  Medical people are simply human body mechanics albeit the down side is more severe.  So why aren't medical workers held to the same standards as mechanics are? 

If my mechanic had caused harm to my car, I could get a monetary reimbursement to cover my out of pocket expenses.  Why can't we get this from medical workers?  Why are they the only (as far as I can see) industry that can get away with causing serious harm (iatrogenic) to people?  Why are the the only entity which can refuse to give a "good faith estimate"?  Why is medical care exempt from any kind of control?  There are a few basically toothless laws, routinely dismissed by medical workers, which are supposed to exercise control over medical treatment, why aren't they enforced like the laws covering mechanics are?  It's unfathomable.  My mechanic can't replace my engine without my consent, why is it that medical workers are allowed to go far beyond the intervention level that the patient prescribes?  We can't always fix it ourselves like we can with mechanical problems with our personal vehicles.