The head gaskets tend to go at 100,000kms, and roughly every 100,000kms after that. To get it fixed professionally it can cost around $1000. If you do it yourself, which isn't really difficult, just time consuming, it will only cost you parts, around $150 - $200 at the most. I will be writing a tutorial on it soon so you can have a look at that.
If the cooling system is kept in check and in good condition, then you shouldn't have too many head gasket problems. They are a reliable car, mine has done around 275,000kms and still running, with no problems.