It is a problem, and when the guides were removed, the problem became worse. The guides helped newbies, and was definitely the best source of info on these older games. Rec.Games.Pinball archived older repair threads. So it was made even harder. If you look hard - or ask the right people - you will find the guides !
Regarding courses - In the "old days", operators had qualified techs - their qualification was usually an "A Grade" Electrician's certificate. You needed BASIC electrical and then electronic training. You also had to be able to troubleshoot on location. Today, anyone can try their hand at basic repairs without the need to understand the electrical and electronic background as there is help available and most electronic faults can be rectified by replacing boards. The idea of training or courses would be very basic, as the tech needs an electrical background, and to teach electrical / electronic theory, you should be a qualified technician or teacher. There's 240V under the hood, and thats something that has the potential to injure or kill.
I think AMD run a course on Stern and Bally Williams platforms - but no one has ever offered an SS course. I don't think it will ever happen.