2005,Burning engine oil and have gray smoke coming from below the engine and the tailpipe.

I bought a car with little oil in it 3rd party. I got an oil change and started to drive home 4 hours away and the oil light came on. I stopped and checked the oil and all was burned after I drove it 200 miles and I added 3 more quarts and it was burned off after 150 miles. There is gray smoke coming from below the engine and the tailpipe. There is no dripping oil on the ground. I took it in to a shop and they said oil was in the combustion chamber(spark plug well I believe). They said I had to rebuild the engine or get a new engine. Is this the only course of action? Is there anything else I