As a few answers, if the Gaiter was showing "signs" of wear, Slight Cracking, the garage was in order by saying Advisor to put him / her self in the clear, the seller should replace the Gaiter FOC Thelewisgang, regards the loss of Grease, what I think the garage will do is clean out the Joint & refill with Clean Grease, the Gaiter is like putting Plaster on to keep the dirt out & the Grease in to lubricate Thelewisgang, I would also ask about the N/S!