Back in 1977 I entered Diesel Mechanic School at the local college. This was the start of my 4 year apprenticeship as a Heavy Duty Mechanic. This first step was called a pre-apprenticeship which would last 6 months. I had never touched a diesel engine before and had some automotive/small engine experience from high school.
...if you're interested in getting into this trade I would go down to the nearest diesel mechanic college or technical school and ask some questions about the curriculum and cost ... I'm content now after working in this trade for 32 years and find myself telling a lot of stories about experiences and aha moments & wouldn't trade it for the world!
Well worth reading the whole story at his blog.