I had the same leak on my 2002 at 180k miles. It just started to leak and put drops on the driveway. I kind of went over boad to try and fix it but after it was all said and done. All was well.
I started with the valve covers and intake. Why intake, because it makes it way easier to get to the oil pressure switch. My big hands don't do well in tight places. When that didn't fix it, next was the oil pan. I had seepage along it on both sides.
So that didn't fix it so next was the rear main seal. Low and behold, once the transmission was pulled back you could see where the leak was at the seal. Changed it out and all was well, nice and dry all over.
Sorry couldn't help much but that was how I attacked my leak.