Came home from an RV trip and discovered water in the shower pan. Found the outside skylight was cracked. The plastic was brittle. I don't recall hitting any objects and there was no other roof damage.
I replaced it with Specialty Recreation K1422ELP Low Profile Single Pane Exterior Skylight Kit from Amazon -
I used the sealant that was with the skylight kit to seal the bottom flange of the skylight to the roof (per instructions), and then used Dicor 501LSW-1 Lap Sealant to seal the perimeter of the skylight to the roof and to also seal the screw heads.
It was a fairly simple task and the skylight fit the existing opening. The new skylight has a much lower profile.