sounds like issues of using an engine that sat a long time, did you at least give it a tune up, use your original coil etc?
if it flashes, it is most likely wires/coil. if the light goes out. If the light stays on, read the code.
even the oil pressure, could just be a dirty old sender with dried sludge from sitting, or could be a sludge fill oil passage/pickup.
Its hard to tell, start by pulling cleaning and replacing that sensor.