to take the head off, its not a BIG job, stealth say about 350 quid, its a matter of taking the manifold's off, doing some cam stuff (taking the chain off) and replacing the gasket. problem with the chains is that the gearbox has to be out. if things are terrible, it could cost nearly 1.2k according to vince at stealth, but he says its excessive if you are under 100k, but since you're over, i'd think about doing it....getting the head/chains done is a job that should be done before it dies.