SETUP:

Our building changes a lot, so we keep updating the drawings at a pretty constant pace. We just had another company do an update of an HVAC drawing. There's a lot to it. If I could simply overwrite our current HVAC drawing for that floor with this new one, that would be easy. But it took some time for them to get it to us, and in that time, we have updated our own files. I can't simply overwrite, or I'l lose our work from the last few weeks in the file.

SO MY QUESTION IS:

Is there a good, safe way to take one drawing, add it to another (by perhaps xrefing it in and then binding and inserting it?) and have AutoCAD automatically remove anything that is being duplicated? The idea here is to import the new file into ours without picking it apart manually (because that takes forever and is subject to human error) and not have to worry about there being duplicate objects on top of one another.
You could say that it might not be a complete solution, because changes in the drawing might also require that some things in the existing file be deleted, but this would get me halfway there in a flash.

So anyone got a good idea?