Granite problem?

Bathroom has a garden tub that I want to take out and replace with a shower. The problem is that there is a glass block window/halfwall at one end. With it of course is various pieces of trimwork that are fine in a tub environment but would be a disaster in a shower. I much prefer not having the window filled in and converted to a wall, as this would involve far too much work, what with the hardiplank exterior and the window being quite high off the ground. To make things more difficult, the builder thoughtfully positioned the window so that they could turn the interior sill into a conventiently placed shelf, which will be guaranteed to turn into a nice pool of water with a shower running. In addition, the window is not centered in relation to the shower and extends beyond what would become the shower wall. My preliminary plan is to tie in to the glassblock by constructing a short floor to ceiling glass block wall at right angles to the existing window/wall. The problem is what to do about potential moisture problems because of all that trim work that has to come out. I'm thinking of replacing it with exterior grade manmade products (picture smooth finish Trex planking) but how can I make sure water runs off and absolutely cannot get behind it?

[FONT="Tahoma"][COLOR="purple"][B]Our master bathroom counter is 57 inches and has 2 sinks. For resale, will one sink work? We have never used the two sinks at once, not even after 13 years. We want to put in a stone counter and one sink Any ideas? :help: