1988 Mazda 626 reman engine

I recently had the engine replaced in my vehicle.
within 5 miles of driving the car the check engine light came on. I drove it back to the repair shop and they replaced the oxygen sensor. I drove the car approx 1k and took back to the shop so they could inspect for any leaks and give an oil change. I drove approx another 1k and took the car to be smogged. It failed the visual smog and was advised that the timing was @ 6 degrees and should have been @ O. I was also advised that the oil was 1 3/4 quarts low. This was 12 days after the oil change. Took back to the shop where they say the timing was corrected and that there appeared to be no visual oil leaks. Plugs were pulled and were white. Smoke is white and stinky/sweet. Never had problems prior with smoke or smogging.