W126 Benz Oil Spec and Other Questions

[Citroënbender]

I normally avoid German cars, but making an exception here. K-Jet 280SE, I think 1984. Barely used or maintained several years, rego renewal coming up early September. Starts readily and generally the functions work.

Q1: Where can I reliably find the current fluid specs? It seems implausible for one site to say 0W-40 FS and another to recommend 20W-60 Mineral. Similarly would prefer to avoid second-guessing other fluids due for renewal by age.

Q2: Nick-knacks and trim: Are dealers here surprisingly affordable, do I go Pelican, or Autohaus Az, or Eastern Europe? Front brightwork and fuel supply/periodic service parts probably the main targets.

Q3: K-Jet (shudder)… Any good online references for real world checking of components, what about injector service or specialists if it’s been tinkered with (I don’t know its status, but am aware of the hellish diagnostic loop where uneducated poking can take it)? Seems to be a couple of pots down by noise/roughness and too soft off the pedal.