diagnostic services

Took my Saab there with error message about gear box. It would not start for me but did eventually. There is a new owner who assured me he was a good Saab mechanic then told me all I needed was a change of spark plugs and filters. He also told me he had done diagnostics and everything was fine. He also changed out a worn strut. He charged over $800. Two weeks later I broke down in the middle of University when I came to a stop light with the same error message. I had it towed to another shop and they replaced the sensor for $150 and works great now. The previous owner was a great Saab mechanic but not this new guy.