Just suddenly today, my 97 Quest 3.0 started running extremely rough, 3 cylinders maybe firing correctly, no codes other than P0325 for the knock sensor, my mechanic said I can ignore that. Today after some fishing around the internet, I cam across this posting about red dust so I took the distributor cap off and it is lightly covered in the red dust. People say this is the precursor, fairly quickly, of the distributor seizing because the shaft is disintegrating. I have nowhere to start, no codes. Is this a forgone conclusion, should I just buy one and pop it in, looks pretty simple?

What about the rotor? Is it made of a carbon fibre PCB with the metal film sandwiched between PCBs? If that's the case, the metal film could have burned into the sandwich, extending the spark and causing it to jump around and burn everything around. I had this issue in the old Maxima but no dust yet, replaced the rotor back then.
Also, IIRC the contacts in the cap are aluminum and the spark creates thick layers of oxide on them, insulating essentially. I had to clean the oxide from the prongs and sometimes slightly bend the prongs towards the center to keep the correct gap. Clean everything you can from the red dust, clean the prongs, check and replace the rotor if necessary, and see if this fixes misfire.

What plugs are you running and how old are they?

far raf is correct. Also, this Van is pretty old. If you haven't replaced them personally, you can assume they need to be replaced. Cap, Rotor, Spark Plugs and Spark Plug wires is the normal maintenance combo for your high mileage vehicle. Replace those all now. Later you can get an oil change, new belts, new air filter, flush the coolant, etc. as you have the budget. Your mech is right, ignore the knock sensor code for the time being. Odds are good that it's old and cracked, not actually detecting knock.

Please let us know how it goes and Welcome to NICO Club!

I find that replacement of spark wires is highly overrated. They usually last a very long time and rarely go bad. This would be the last item on my list of things, with the rotor being #1 and cap #2.