there is a tutorial from Billy called Cleaning your vintage machine part 2. He gives the low down on cleaners and the how to. Even though you have "sinned" if you haven't seen this tute, it is good. I bookmarked it for my Singer 15-91 and to clean my treadle. He lists what exactly he uses, but gives pics for how he uses them.
Good Luck!
My guess is that Murphy's Oil Soap would do more harm than good. I was told not to use that on my wooden cabinets and floors if I want to keep a finish.