Ok. For a building that is a high poly I think. But I guess it all really depends on what it will be used for by the buyer. If the building will be a standalone building then it would be low. I would leave it where it is poly wise.
As far as the fascia…change it from pure white. More yellow or brown in there. Little tip. Never ever touch the sides of a color wheel. There is not pure colors in the real world.
As far as the normals. Easier for you to find a tutorial than for me to add a lengthy response explaining how to bake a normal map. the short end is it can be found under the render tab and has to be done in blender internal render engine not cycles.
Now as far as the stencils you have now. To add some sweet weather effects automatically…insert the brick texture or your uv map with the brick texture, into photoshop and create a new layer above it. Create your text but you only want the selection of the text. Switch to bucket fill tool and on the tool bar at the top of the screen there should be a box that can be checked that says all layers, click that then bucket fill. that allows photoshop to use the contrast of all the layers to exclude areas to paint…nifty!