oh dear...
you'll be pleased to know that both Ran Man and lostclimate are wrong. in A7 (which i'll assume you're using because you didn't mention that you're using an old version of gs) you can compile a level with the "create meshes" flag or something like that, and the performance is fine. without that flag, level polygons are sent to the shader one at a time which is really slow.
i haven't used shaders with blocks, though, so i can't tell you exactly how. but the manual is your friend, and i found this -->
http://www.conitec.net/beta/ad3d_automaterial.htm <-- which looks useful. in the next update, however, you'll be able to assign shaders straight to WED blocks without using d3d_automaterial.
additional textures (like bump_maps) would be assigned by material skins. this means until the next update is released, you'll need a separate material for each level texture.
julz
