You should be able to disconnect the grey wire from the ignition coil. In that state, with the points open, there should be infinite resistance to ground.
Both of the mag coils have a very low resistance.. less than 1ohm, IIRC.
The condensers are a common problem. If you haven't already replaced it, you might as well go ahead and do it - you're going to need to anyway, soon enough.
I have an internal diagram for the pre-78 bikes, but not the later models. And of course, they are different.