No need to replace the top on the z3 - you can replace just the plastic window. It's not a difficult job but it's tedious starting that little zipper just when you get one end on the other comes off and so on - make sure you drink decaf that morning! Otherwise it's easy.
Renovo didn't do much on that old window that Plexus did not do. Since I have it, I will try it again as the need arises. If I had to buy more right now, I'd try something else. Probably Novus based on what I've read.