as far as turning multiple object into a single object it's as simple as exporting them as a wavefront object (checking all the parts you want in the object in the hierarchy popup during export) then importing the resulting single object. but remember that when you do this it becomes an unboned mesh with no morphs the only dials are scale rotation and translation so if you are doing this to conforming clothing it is best to conform it to the figure before exporting the object just make sure the underlying figure is not checked in the hierarchy when you export.