A good mechanic is worth his weight in gold. I my mechanic's case, he's worth more since he's such a little guy.
I had a flat tire. Long-Suffering Husband and I jacked up the car, changed out the flat for the crappy donut spare, and I brought Mechanic Nick my flat tire. He found two rim leaks, popped the tire, cleaned the rim, re-seated the tire, replaced the valve, and aired it up for $15.00.
It's way too easy to get taken by mechanics. I will be very sad when Nick retires.