Need to update large MusicPlay site from 5.2.0 to current and I'm scared

Do I just follow the update instructions, and do I follow those from the documentation in the theme download, or the sticky topic up updating? I don’t see where or how to see if I have a child theme. Any assistance, or direction to a guide would be helpful, we are techs, but not webdesigners. If incrementally updating would be safer we are willing to do that too, we just need to know where the incremental files are to slowly come current.

Thanks!