So it sounds like you already have it changed. If not, loosen the big nut in the center of the shaft near the carrier. This lets you collapse the shaft so you can replace the disk.

Be careful not to let the shaft slip apart, but if you do, there are marks on the two pieces that must be aligned when resplining. There are two knots on one piece that align with one knot on the other piece.

Those are great big bolts on the disks, you don't need to torque them, just tighten them real good.

Good luck,