The spring and carbon brush are available as replacement parts several places on the web; Sew Classic and The Featherweight shop are additional two, and ebay have a few sellers. A local repair shop might have them too. If you take appart the motor you might be able to use some kind of solvent on the grease wicks and grease the ends of the bearings directly. In general grease wicks are standard replacement parts too.
A trick with a clogged up grease wick is to give it one drop of oil, run the motor, let it warm up and see what happens. One or two drops (literally) will not seep into the motor but just enough to reach the ends of the motor axle; it can take time if the wicks are very clogged up. If the grease wick faces downward it's harder to get the oil to seep through; you have to get clever, run the motor up side down some how. It's a bit dangerous to give advice like this, because you have to be very accurate and never over do it; people will easily get this wrong if advice like this is spread about.