cyl head gasket blown how much should i expect to pay

hi my disco 2 v8 cyl head gasket is blowing , i first thought it was a hole in the exhaust as it was making a lot of noise but got it checked out its the head gasket ,how much would a garage charge to do this for me about ,thinking of getting the two heads skimmed and new valves if needed any help would be much app thanks g

I recently paid around £600 which included injector seals being changed and full service. this was on a TD5

thanks for the reply my mateis doing it for me doing both heads while its all off got price to scim both heads and new valves £250 so happy with that thanks