Front Differential exploded!

Hey guys, my 2000 4.7AWD Durango's front differential exploded yesterday, it has cracked the casing all the way around, i guess something got jammed? The front two wheels just started locking up simultaneously then releasing, and since the roads here are covered in snow the truck would slide.. I thought maybe the transfer case was going but i guess it was the diff. What is entailed in replaceing the diff? rough time/cash estimater? I'm trying to figure out if its worth it on this truck as it has 318000k and is my winter beater (although i've had it since new) Thx Brandon