Well one thing you need to do now is be right on the retailer's ass. Headgaskets are not expensive themselves, but the labor will be. So you need to keep pushing cause it all depends on how hard they work. You may also need to look at the car's service history, mileage and how your driving style may have affected it.

If service history indicates no problems, the car isn't too old and the mileage is <150.000km a headgasket really shouldn't just fail. If it's one of the Audi models with a TSI or turbo engine they're a bit more likely. So best check these things to see if you can push any liability onto the retailer (saving you money).

As far as driving style goes, if you don't let the engine get to temperature before you start giving it the beans you risk damaging it, a "sporty" driving style will increase risk regardless.

On to the costs. Assuming parts and labor are about the same as here in the NL it will probably set you back around €1000. The cost can however be much higher if the gasket leaked enough to starve the cylinder of oil. So tell the retailer to check for any damage to piston rings, piston heads and cylinder walls while the engine is open. Diagnosing any problems in the cylinders then might save you money later.

Of course this is all assuming it's the headgasket, but my money's on that .