tentioner

Hi guy i am thinking about changing the tentioner on my c240 v6 as it is getting very noisy, can anyone tell me if this is a hard job or one to be left to a mechanic?:confused:

just changed the head gasket and all is fine except i noticed some material has come off the tentioner and i think the chain is to tight? i removed the plunger to take off the cam sprocket and put it back in again? has the plunger got to be set? and is there an easier way of replacing the...