Vectra 1.8 16v - Head Gasket + Camshaft -?

I've had a tapping noise coming from my engine since I bought it - I've been told this is the Camshaft. Just had the exhaust replaced, drove home and it overheated, apprently Head Gasket's gone. How much should this cost to have done (Camshaft & Head Gasket)?
Is it worth it, I paid £1300 for it in April 2006?