The rollers certainly needed replacing:
Note the pipe cleaners holding the automatic ribbon reverse mechanisms closed. If they are both open, the mechanism jams.
... and dunked, along with other parts, in rust remover (Rust911 concentrate will make 16 gallons and works great).
The carriage had to come off too. This is easy once you know the trick: the upper carriage rail slides out once you remove two long screws from the back. Then, carefully observe the location of two ball bearing holders. One of them keeps its bearings secure; the other is separate from two bearings which you obviously must not lose.
One of the links between a tabulator key and the tabulator was missing. This is a common problem on L. C. Smiths. As I've done before, I replaced it with a length of wire from a clothes hanger.