Front Diff Rebuild Question

I took my '03 to 4W Parts in Raleigh, NC to have wheels and shocks put on. While doing the work they noticed noise coming from the front diff. I just called a local shop, and they'll do a rebuild for $1100 (parts, labor, fluids).

I don't have experience with this kind of work. I've had this truck since it was new. I'd like to keep it running well for another 15 years if I can. Does the rebuild seem warranted? Does the price seem fair?

Thanks!