Could you provide some examples of "parts and mechanisms" that only professionals could fix on 1970s era cars? Also, how much experience do you have working on

Could you provide some examples of "parts and mechanisms" that only professionals could fix on 1970s era cars? 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.