There are some really good tutorials here on the W124 500E board. For one reason or another they have a sub board for the C126 coupes and have some great tutorials. Many of these tutorials are equally applicable to the sedan.
https://www.500eboard.co/forums/forums/c126-how-to-tutorial-articles.63/
https://www.500eboard.co/forums/forums/c126-how-to-tutorial-articles.63/