Their are a variety of things that may be wrong, none if them are particularly cheap. Generally a body shop needs to handle bent frames depending on the severity of the bends. The alignment is most likely also bad which will increase wear on the tires and potentially destroy the axle in the long run. Its terrible to drive with a bent frame.
As for the knocking in the engine. Does it sound like its coming from inside the engine block? Or is the entire engine moving around as you brake/accelerate? If the noises are coming from inside the block, that isn't cheap. It generally means something in the engine broke off and it constantly bouncing around, causing potentially even more damage. The extreme heat of not having a radiator may have caused this issue in the engine.
If the entire engine block is shifting around it may need new motor mounts. Their are a total of 3 of those holding an engine in. And if it's to the point were the whole block moves, they all need to be replaced. Each one runs about $50-100. Plus unless you have a lift to pick the engine up a repair shop would have to handle it, costing even more. Damaged motor mounts would have been caused by the sheer impact force and driving with the bent frame/bad alignment.
