Changing the turbo chargers on this engine requires taking out the engine about $3000 total retail cost for the turbo chargers, about 3 hours to swap out the turbos once the engine is out and probably 20 hours to pull out the engine and reinstall. Extreme cold would not "cause" the turbo chargers to fail, infrequent oil changes, or use of poor quality oil would cause premature failure. Use of Synthetic oil in these engines is important. Before assuming the worst see if there is an Audi specialist or dealer in your area to get an expert opinion.