Charity B

My car, a 2001 AWD Sante Fe (with only 91 000 km) was in for its MVI & oil change. At that time, the mechanics noticed that the car needed a new pinion seal & was leaking fluid. Apparently, when they replaced the seal, they noticed a larger problem (not fully explained to me). They tell me the fluid was dirty & ressembled molasses. They also tell me I need a new REAR DIFFERENTIAL. My car, which had being running quietly, now sounds like an airplane whenever I take my foot off the gas. Can someone please explain a) why its loud now (with better fluid) and b) how a car with low mileage, no off-roading & regular "check-ups" at the dealership could get to such a state that it needs a new rear diferential.

Also, does this pose a safety hazard until I am able to get a new differential. I travel with 3 small children & don't want to drive an unsafe vehicle.

I'll be there on a cruise & have an excursion planned for the afternoon. I'm curious as to how to spend my morning. Any shops / attractions that are "must see"?