1997 Other Oldsmobile Models busted CAM/blown head gasket

I originally brought my Olds. Silhoutte into the local mechanics for an overheating issue. They replaced the head gasket for me ($1800 later). My wife drove down to the next town, it starts sounding like it's firing on 2 pistons, so she shuts it off right away. The tow truck came, took her and the vehicle back to the original shop. They warranty their work, according to them. They looked into the problem and said it was a busted camshaft. They also said it was a "coincidence". I don't buy that. They also said for another $2500 they could replace the cam but it would be a bandaid fix. Never heard of a cam breaking on a grocery getting van. They are part of the small business bureau. I've been pondering on sueing, calling BBB or just kick and scream until they do something about it. Any suggestions?