i am task the same project.  but the terrain itself was made by my co-worker who is a civil engineer, knows the elevation of the site we are working on. I was bug down with his high tri-faced terrain (170,000 )
Yes that is a nice idea to start with. Terrains with almost flat requires low poly face while vice versa for the detailed portions of the other portion of the terrain. max smoothing features will work fine once you smooth en the parted terrain to soften the terrain model (turbo smooth) pay attention to iterations.  texturing -make it planar i think if you can give it a bump map much better.  if you are making roads on it, separate them so you dont bug down yourself on assigning to ids to the faces of the modeled terrain.

I agree.  my scene blew up its poly count when i imported my co-workers terrain, coupled with slow realtime viewport panning and zooming.  now im afraid i have to redo his terrain over or delete some to bring down the poly count and have a neat quad mesh,