Maybe not the most popular choice, but I would just spend a couple hundred and pick up an EM game if you want to learn. Very simple electronics you can easily learn to read schematics and trace back and isolate issues. It would be a bit less of a learning curve not having to deal with integrated circuits and the possibility of board repair if you are new to soldering. None of the basic playfield mechs have changed a ton over the past 50 years, so all of that will still apply to modern games.

Use the money you saved and just buy whatever game really interests you and that you like playing. I would not let any hesitation about possible future repairs stop you from buying any machine that you liked.