I have returned stuff to GC in the past, and found them helpful and approachable.
They do, however, try to run a tight ship and won't replace your stuff if you, say, mis-connect a battery and blow an ESC. They argue that they are cutting prices as far as they can go, and haven't got any slack to replace goods as a kindness to the customers. If anything is their fault, of course they will sort it out....