Late last year, I heard FRPP had switched to some sort of "chrome plated" ring and pinion and the same guy that installed my gears in Feb '07(mine was nearly the 30th S197 gear swap he had done and never had an issue...to date)was having all sorts of noise issues with almost all the newer FRPP gear sets.
+1 on paying a pro to do it if you're not sure on how to do it yourself or don't have the proper tools! It was well worth my $300 labor to have been very close to 40K miles of noise/trouble free driving with the 4.10s!