The only thing about having an oil pressure guage is for the peace of mind that the oil pump is working or hasn't failed. I like it for the assurance it affords. When first started, you may get maybe 10-15 # but when warmed up and driving at road speeds, you will only read 2 1/2-3 psi...
If it were me, I would drop the pan and remove the valve cover. I would look closely at how the pan and valve chamber looked. Lots of crud,clean well and consider non detergent. If not crud , definatly use detergent.