I'm sure there's more confirmation of this out there other than what I'm about to write:
I visited a local Rivian shop and the sales guy tells me he suspects it will not be as easy as a traditional ICE vehicle but should be somewhat accessible by owner... I'm not too excited about that...
Here's real desert-world feedback on glass roof life: we've driven our Mach-E for 4.5 years now in Phoenix AZ with no heat complaints from either driver, and I have HDS (hair deficiency syndrome). I won't hesitate on glass I think it's great. I suppose I'm assuming Rivian's glass formula is...