For they shiny metal bits I find pastes does a better job than liqids, there are lots to choose from; Quick-Glo clean and shines with out being smelly, that's just one of two or three I keep in the cupboard under the sink.
You can reverse the Revco addition, but I think you need to track down the missing parts, I remember at least two previous posters who found the Revco additon to be a bit noisy compared to the original setup.
I'm not sure about the motor, it's a bit different from my Singers, but there might be a carbon brush under the black bakelite screw. There is a motor axle carried by two bearings on each side, and it shows as the protruding point at each end of the motor. The bearings usually takes grease, but on some models it can be one or two drops of oil.