even if you have the shop do the work - make d@mn sure they coat the new rubber plug with high temp sealant - the book does not tell them to do this - so many leaks I believe are caused by the dealers at the first service - what happens is without sealant the rubber sticks to the head due to heat - when they pull it out to re-torque the head bolt under it part of the rubber sticks to the metal - after the re-torque they just poke it back in the hole - it's like a rubber stopper - at that point the plug is prone to leak - it's really a one time use plug when sealant is not used.