I believe it'* an instrumentation problem:
The oil pressure gauge reads close to 120 psi and there are no other apparent symptoms. The reading does vary a little with engine temp and rpms, as you would expect, but stays way above normal.

The self-test after starting the engine seems normal, from what I remember. (Gauge goes to max, then min, then settles at the measured pressure level, normally 40-60 psi, but much higher now)

Ideas anyone?

need a oil sender switch try rock auto

That'* what I guessed. Where is the switch located?

just above the oil filter

Thanks Steve..."You da Man"

$30 at your local O' Reilly store as well

Check the plug first. Might be loose or corroded. 120psi is no signal from the sensor.

Thanks Guys,
One more dumb question:
If I do have to replace it, I suppose I'd wanna do it during an oil change to avoid a mess, right?

during an oil change would be best however if you did it other than at time of oil change only a little will leak out

Yeah, even if you do it during an oil change after the oil has been drained some will come out of there. It'* not a lot either way though.