Last summer I was able source genuine Porsche glass top (2003 S) from junkyard for 350$, and it took me 1-2 hour to remove (2001 S) original top and drop a new one in place.
I have decided to order the Sierra top w/glass in the German material. I don't know if spending the extra $300 is worth it? I hope I don't kick myself. As for the install I am handy and have a decent tool set I think I'll give it a shot.