'92 3.8 APV Oil Pump???

400,000 + and still going... but I think that my oil pump is going. Pressure has dropped and there is plenty in the pan. There is a tapping sound up top that paces with the engine rev and the sender unit has been replaced. Could the filter be gunked up as well??? Where is the pump located on the 3.8? Under the timing chain cover or in the pan??? Would love any help. Thanks!