2000 8.25 ring and pinion question

My completely stock '00 Jeep's rear end with 55K has had some gear whine and vibration so I took it to the dealer today. I was told they will replace the ring and pinion at no charge (still under warranty)
my question is, will this fix my noisy axle and the vibration or could there be other problems? Also, what does a job like this normally cost?
oh yeah, the service manager recommended changing the fluid on the chrysler axle every 12K no matter what. He's seen too many of these Jeeps come back for this repair.

i am not aware of any serious problems with the 8.25 but that doesnt mean its not common at the dealers.. 8.25s are known for being "loud" with some brands of aftermarket gear sets though.. i'm curious if they will do the R&P themselves, or farm it out to an axle shop..