A blown head gasket and rattling smoke from the front driver's side strongly suggest significant engine damage. While it *might* be repairable without needing a whole new engine, it's highly unlikely. The rattling smoke indicates internal damage, likely from overheating and/or coolant mixing with oil. This could mean warped cylinder heads, damaged pistons, or other internal components needing replacement.
You almost certainly need a major engine repair. The cost of this repair could easily exceed the value of the vehicle, especially depending on the car's age and make/model. You need a qualified mechanic to inspect the engine to determine the extent of the damage before deciding on a course of action. Replacing the head gasket alone might not fix the problem if other parts are damaged.
