I just wanted to replace the chain, but it was too dirty, so I disassembled and cleaned it.
Derailleur disassembly and cleaning
Front and rear derailleur cleaning
Crank cleaning
Wheel cleaning
And I removed rust from the frame with a stainless steel pot cleaner and gave it a shine.
The o-rings that prevent noise from the wires hitting the frame were all worn out, so I ended up disassembling all the cables and replacing them with new ones.
I finished adjusting the tension of the shifting cable during today's test ride, so I'll be able to ride it seriously starting next week.