Reading about the costs under "Common Fail Points And Fixes" in the article below makes reworking a D-Jetronic system that has been sitting for 20 years a bit financially daunting.
What is the likelihood that I'll need to replace the Engine Control Unit, Manifold Pressure Sensor, or injectors? Are the costs actually that high for parts? Can I refurbish these parts instead or replacing them?
https://www.hemmings.com/stories/your-quick-guide-to-the-bosch-d-jetronic-k-jetronic-and-ke-jetronic-fuel-injection-systems/
re:What is the likelihood that I'll need to replace the Engine Control Unit, Manifold Pressure Sensor, or injectors? Are the costs actually that high for parts? Can I refurbish these parts instead or replacing them?
Ive replaced one or two of these parts along the journey, although not at the one time. I've managed to find good used ones (The parts you mentioned) from time to time and bought them regardless of whether I needed them. Like most long time 116 owners, I have a good supply of spares (like the parts you mentioned), just in case.
The engine control unit is the only one I have replaced (2x).
I have 2 spare sets of injectors cleaned and ready to go. The day will come!
I'd recommend reading through these articles, it's contains a lot of information about D-Jetronic in general : https://jetronic.org/en/d-jetronic (https://jetronic.org/en/d-jetronic)