I think the sender itself tends to leak through the wiring thruhole more often than the o-ring seal. I removed mine, cleaned it up well, and gob'd JB-weld around the wire. Been oil-tight for a couple years now. But mine is the 103 six, and a piece of cake to pull out - if you have to pull the pan on the V8, then you might not want to try the McGiver approach. New sensors are about $50 I think.

If the pan is off, you could check on the bearing wear status, and clean the oil pickup.

DG