Just did mine.
Just takes lots of patience. Did it in an evening.
There are actually 3 parts to the skylight. The outer dome, a plastic decorative inner part (that probably has some purpose..), and the inner dome.
Be very careful and measure the outside dimensions of the flange. I found a replacement from Icondirect. Seems to be good quality. Shipping was too high, but I had to get it done.
I put a fresh "patch" of Eternabond tape around the hole, then caulked a bead of skylight sealant on the skylight and screwed in place with stainless steel deck screws. Caulked sealant around edge and on screw heads, then put more Eternabond over that...
I also had to fix a factory screw up. When they screwed the plywood down they crushed the seam where it met the skylight hole. I removed the two screws and built it back up with shims, then replaced the screws.
Came out great. Toughest part was getting all the old caulk off but it wasn't as bad as I thought it was going to be. I'm sure others will have tips to make it easier.
Max
2010 Silverado 2500HD Duramax/Allison Crew
2000 25' Sunnybrook
2010 Honda SH150