Your model looks a bit too elaborate, you will probrably want to merge away some of those polygons, EM4/FR does not work too well with overly complicated models, remember it has to load everything that is on the map so every polygon adds to the load on a computer. The roof in particular is a place you can clip away a good deal of polygons without the model getting damaged in the process. As for the other part, welcome to Digital Rights Management and all it's stupidity.
I dont know how to reduce the poly # in zmodeler, I do in gmax though. Anyway, here is the progress so far:
Anyone know how to fix those cracks? I tried vertex welding and it didnt work.