Compile mesh

Hello i have some cad model like this http://skfb.ly/54jiedc0a to texture it like this http://skfb.ly/5lk4jd0 i have to generate simple mesh from original cad file. Automatic file converters gnerated very bad mesh, its mesh is posible to texture but its boring and very slow. I try to generate mesh automaticaly. Now i have one definition that generated not bad mesh from the simple cad model (not original but its not problem now). When i try to clean mesh the Blender welded closest point in all directions and i needs use small weld increase and still have more handed work.

Now i can welding only points that have same z level and i can use more weld increase.

But what next? How recreate mesh? Compare point of old mesh with new point set? What about normals?

Cad file and definition there https://www.wuala.com/Arredatore/grasshopper/net/?key=4huG8wjRx2QO