blender is the new one for me lol and I got to say I wish I had started with it much much earlier (woulda saved me a fortune lol )

not had your problem but my work flow is to give each part its material (named as the part) then in poser select that material and then load the map and it all works fine

to make the car doors etc open/close its needs to be rigged as a figure or can be a posable prop. For something like a car where u need lots of moving parts I think it would be best as a figure, each part needs exporting alone then importing to poser one after the other until u have them all in poser, goto the hierachy editor an drag an drop each part onto what will be its parent eg door glass onto door then door onto car body once you have it al sorted hit the create new figure button and it will make the cr2 in the new figures folder then you need to set all the dials to do what you want them to (rename-set limits-delete if you want to) most can be done in poser or in a text editor (is poser specific tools to make it easier).  you should (if its for the market place) extract the geometry and place it in the geom folder(again is tools to make it easier "pose tools or poser file editor do it with one or two clicks and even set the paths for you

hope that helps and I haven't said everything you already know, happy to have a look at the obj or blend if you want me to, pm me for email addy