What could be the cause of cylinder misfire on a 2002 Honda Accord?

Yesterday the brother of my brother in law looked at my car because he works with cars. He noticed one cylinder was not plug in and then he began rearranging the 4 cylinders as it looked out of place and told me to start my car. It wouldn't turn on and he kept rearranging it until it turned my back on. And then I went and drove some and my car started shaking, which it hadn't done before. The check engine light wasn't on before. I got the codes checked and majority of the codes state a cylinder misfire. My car was working fine before and tomorrow I'm booked for a diagnostic test. But I feel like the problem might be very minor and I don't want to shell out lots of money for a test that they may not do anything

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