I would suggest (assuming the battery is in a good state of charge) grabbing a multimeter and wiring schematic and start tracing things out (starting at the starter motor).Backtrack wire to wire until you find voltage.As far as oil pressure is concerned I would remove the oil pressure line from the gauge and have someone hold it in a bucket (cover with rags to avoid splashing) while you or someone else primes the oil pump with a hand drill and primer attachment (this will verify oil pressure to the gauge).Good luck!