A model like that is made out of parts, in Poser go to the Hierarchy Editor and make only the part you want to export visible, then export that part as OBJ. You'll have to reassemble the building in VUE but that's part of the fun. Btw have you tried exporting the whole model as 3DS, imho VUE has less problems with 3DS when it comes to really large files but there are loads of VUE users who disagree :)