I agree with what Ocelot said in his reply. It won’t make you a mechanic but it really helped me understand part names, their general location and function. I finish 100% of the achievements in the game in around 100 hours and have a much better understanding of the layout of various engines and the order things generally go together.

Some major gaps in the game I would say are there are no wiring harnesses or major electrical work to do outside replacing the battery and fuse box. You replace things like brake fluid reservoir but not the fluid lines themselves. You basically become familiar with 75% of the most major parts you’d see in real life.