Help you guys, i am trying to figure out whether or not i actually need to replace both left front and right front axles or just the axle boots. I noticed that the axle boots on both the left front and right front axles had torn and that the grease has begun to leak. I took it to a mechanic and he said that i would have to change the axles on both side... but im' not sure i really need to change the axle or just the axle boots. any suggestion as to how i could decide what exactly needs to be changed?

And if i take it to the dealer should i just get an estimate and leave while having them tell me what needs to be changed so i can have an outside mechanic do the work?

2003 bmw x5 3.0 90k miles
Any help would be appreciated.