2000 Chevy Blazer Engine has a clicking noise.

I will start from the beginning, My blazer blow the oil gasgets and oil was all over the street, I took it to GM to get fixed and it got fixed, a coiple of weeks later I got some other non engine items repaired regular maintance done and then I could hear this ticking in the engine, out to Gm again, and a day later they called me and told me the head gasket must have a crack, from the noise they could hear, they did not even open it up to look, but thr truck does not over heat it still drives not much power but it will go, the engine does shake when it runs, everyone just says to replace the engine without looking at it. I thankyou for any information or thoughts you may have to steer me in the correct direction.
Thankyou, Bob