Oil pressure issue
 

2002 ISX-oil pressure gauge fluctuates, up & down,
Engine never shuts down. Runs great
no power loss. Oils only 2 weeks old.,
Thinking oil breakdown or filter problem. Maybe
Sensor problem. Am I on the correct path?

for the cost of an oil pressure check at a garage is money well spent. this will determine if it is a sensor, or a bad dash gauge.

could be a oil pump going bad, could be a semi-blocked pick up screen.

you do not mention the miles on the engine.

If it started doing that since the oil change, I'd look at the oil and make sure they used the correct weight and filters. If the pressure was fine for say the first week then started going wonky I'd suspect a sensor, either way I too would have the pressure checked and verified with a mechanical gauge.
You also didn't mention how much it fluctuates, some is normal.

The oil pressure sending units are a known weak link, I just replaced mine in my CM-871 ISX. They are around $20, easy to install, a good place to start. So, what was the issue?