model from messed up building polygons converted from gis

[fishingwithjon]

short question: I want to extrude hundreds of polygons downward but there are problems:

 

I am trying to create a model of a large city. i have all the buildings as polylines which are at the elevation of the roof of each building, but they are very complicated outlines and the vertices are totally messed up so they are not planar. I started using 3ds max to take each polygon, select its vertices, make them planar, detach the outline, flatten the outline, then extrude it up to where it looks accurate, but I am a beginner so this seems like a very complicated way to do this. Maybe it would be better to flatten everything first in autocad, then extrude them one by one... but the flatten script seems to lose half of the lines. Autocad 2009/3dsmax 2009.