Yes on the Rebuild.
Fastlane sells a new spring and valve kit with 2 springs and 2 valves.
However, you want to inspect the inside of the Pump under that big nut. The Pump spring sometimes breaks. If the spring is broken get a new one from a Bosch Autorized Fuel Injection Shop.
Someplace there is a thread with a pic of the pump taken apart. Can't help find the pic as I managed to erase my notes.

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84 300D, 82 Volvo 244Gl Diesel