They are easy to work on, usually just light cleanup and relube gets the mech going. Ribbon either needs replacing (if plastic type) or can be rejuvenated if it’s literal ribbon (cloth type), what worked best for me was reinking with stamp ink and once it’s dried out, sprayed the ribbon in cart with thin oil: just ink alone dries out and it won’t print. Now prints very well. However an other printer with plastic type used up ribbon I couldn’t get to print well after trying to rejuvenate ribbon, so likely need to find unused replacement, or replace ribbon itself with cloth type. Either way you will need to pry the cartridge open.