I just finished a UDEMY Service Now Developer course
https://www.udemy.com/course/servicenow-201-development/learn/lecture/7334002#overview
This was an excellent course, the instructor had clearly been working as a ServiceNow professional and I would recommend this course to anyone who wants to jump into development on the Service Now platform.
The coding portions are all JavaScript, so you need some experience in that language. ServiceNow is such a huge platform that I think being able to develop applications within it’s framework would be necessary for any medium to large company.