I've had a head gasket failure on my car. It's not the end of the world - expensive to fix, but not horrendous (provided you realise it's blown and don't overheat the engine. If you don't realise, and badly overheat it, ultimately the engine can be scrap).
Once it's done, then should be solved - the failure is apparently down to the gasket quality in the mid 90's.
Personally, I would be more concerned about other areas - many cars on the market are in need of substantial suspension and brake work and/or hydraulic work to bring them back to factory spec.