There are no professional software engineering licenses. If some software is too important for Joe Public to wrench on, it should need to be signed off by a P.E. who can vouch their livelihood and professional standing on the quality of that software, representing not the company's "maybe some people will die, but we can afford it" interests, but the public's "we don't want manufacturers planning to kill people" interests.
Until then, I've got the same qualifications as that person. Let me at it.
What?! Those parts were frequently repaired/replaced by non-professionals. Half of the Craftsman section of the tool department at Sears in the 70s and 80s was mechanics tools so you could exactly that.
Also, how much experience do you have working on cars? The reason I'm asking is that a lot of repair and maintainance jobs may seem hard if you've never done them before, but are actually not that hard.
The 1970s car had a ton of parts and mechanisms only professionals could fix. Not being able to touch car software is good, and demand will dictate how many cars will cater to your ideology in the future. Probably not too many.