Definatley not a diy job as the tools that are requred are immense. the heads normally warp on thes if driven after the gasket has gone. but the biggest problem that John has mentioned is the injector,s sticking in and for a firm to come and get them out is around the £250 area. Then the price of the new parts (possible second hand cylinder head ) timing belt, tensioner, guides, water pump, antifreeze, oil, service parts and replacement injectors and the labour cost often make it more viable to just sell it spares or repairs or look at a second hand engine sorry for the bad news. p.s I have removed your registration mark and most of your vin from your posting just to be on the safe side