[WelmoedJ]

Additional information on the problem:
Last week I was close to home when the oil pressure dropped to zero.
Almost immediately I noticed the hydraulic valve lifters to get noisy.

Now I have the problem that testing the pressure obviously is no longer possible.
I intend to pull the oil pan and the oil pressure/fuel pump switch.
What's left in the oil pan will help to decide what to do next.
It also helps to determine if I do or don't need to get the oil pump rebuild kit (besides a new oil pan gasket, perhaps pump screen).

I'll keep you informed of the results.