[shorod]

Per the factory service manual for a 2002 LS, "NOTE: The roof opening panel is available as an assembly or a track and rail assembly. The track and rail assembly must have the roof opening glass and the roof opening panel opening shield transferred from the old unit. The roof opening panel assembly can be installed without transferring parts from the old unit."

I'm not sure where the best place to purchase this assembly would be though.

As for the difficulty, if you send me a private message with an e-mail address for you that can accept attachments along with your request, I'll send you a couple of PDFs on the procedure.

-Rod