Hi Rob!
Thank you so much for helping me out this detailed 
Apparently so, yes. From the looks of it I can't seem to find anything more complicated to the mechanism than this - considering it's a consumer machine from the late 50's, this might even hold true.
Since it's a cheap part, I'll additionally use the rectifier bridge. If the Schmitt-Trigger is needed, I'll add one, but for now I'll try with as few parts as possible to not make it too complicated for me.. been a while since I've fiddled with electronics
Yea, that's pretty much what I was planning to do. Then once I have the correct sequences, it'll just be a matter of deciding on which device to decode them. I'll probably do it on the arduino, since I'm not too sure about sending time-critical data via bluetooth, although after some tests it shouldn't really matter.
As for the opto-coupler itself, I've been looking at this one:
http://www.produktinfo.conrad.com/datenblaetter/175000-199999/187038-da-01-en-PC817.pdf
Though I'm not sure which ratings to use to calculate my resistor values, etc.. Reading these data sheets is indeed quite hard.
Greets,
Philipp