replace the head gasket or put in a rebilt engine

I have a 5.7 liter GMC engine in a 18 foot step van. I drove the truck home to ohio from Florida. 1,200 miles. No over heating at all. The engine burns a lot of oil over a quart and a half per tank of gas. There was no smoke from the tail pipe. I did loose some coolant during the trip home. I let the truck sit for 10 days after i got it home then drove it to a tire shop for some tires. During the start up it did not smoke. After 2 minutes running it started to blow white smoke from the tasil pipe. This stopped after jusrt a quarter mile of driving and did no more smoking. I tire shop feels there is a blown head gasket, and has suggested a rebilt engine because of the oil consumption and poor performance of the engine running. It does missfire a bit and the service engine soone light stays on the cose is amisfire I am told. Should i replace the engine or just go to have gasket replaced and heads machined is needed.