I'm considering the purchase of a 2001 VW Golf TDI "mechanic's special", so named because it apparently has a failed head gasket (white smoke). I'm not a mechanic but I'm fairly handy with tools and figure I could probably fix it.
My concern is that head gaskets are not the kinds of things that just fail for no reason, and that this one might be the result of some problem that has done other damage to the engine or other parts of the car. So I'm wondering what the likely causes of head gasket failure might be, and what other damage those might have caused.
Bonus points for indicators of these problems that can be seen without splitting the engine first. :)
Edit: 225,000km (140,000 mi), if that makes a difference.