You can change the valve stem seals with the head on by using some some ingenuity and made up tools or remove the head and strip it. I have tried both and would recommend the head off as you can give it a clean up and replace the head gasket also. Don't know of the labour cost but it is a good days work and you can price the gasket set from Stuart in the Euro Car Parts forum. Recommend the timing belt and tensioner are changed also.
Steve.
