The stock guages normally suck, and on top of that at idle an L normally generates 10ish psi of oil pressure. Could be a reason its reading next to nothing.
As for the oil change, Chevron probably used their crappy brand oil. If you're just driving around town it should probably be fine, but I would never take it there. You should find out what weight oil they used. Probably 10w-30 or 5w-30. Service manual says 20w-50 for reference.