Im trying to change my oil. Where can I find the oil filter on my 1998 ford ranger??

try looking inside the frame rail , directly under the drivers seat (outside of course) .

I found out with my old 94 Ranger 2.3L that the oil breather does not have a filter element, which causes oil to "naturally" (as Ford puts it) accumulate in the throttle body and air intake hose. You can get an inline breather element at any parts store for a few bucks and install it on the breather line without harming anything, and this will stop. Cheers.

check coolant temperature sensor

Very common problem, some 2.9L were mechanical lifters that required adjustment, others have trouble with the hydraulic liters being noisy.

try installing a oil pressure sensor
or
check see if you have a oil sensor which is for the light and not the gauge
hope this helps.

change the oil pressure sensor.

Transmission needs sychronizer rebuilt

Check the lowest part of the oil pan (under the engine)( yes you have to get dirty for this...) the bolt is decievingly small... and facing to the side or angled downwards.

changed fuel filter lately? changed air cleaner lately?