what is the chance of a head gasket failure in under 5000 miles?

What is your question?

I was told the head gaskets, timing belt, pulleys where are changed before i got my car. I have a major hydrocarbon leak in my coolant and get random overheating. I was also told that they replaced the radiator but when the connector for the upper radiator hose broke off from the radiator i question it was done since to was supposed to be not even 6 months old. I am looking to see if there is any help out there for any of this?