Well, from what I've read, the VC model is seperated from the exterior model in FSX.  This means that if you replace the interior model (somewhere in the Model folder) with another one, it makes the interior different.  I would assume that you need to also edit the panel.cfg file for that particular aircraft to make it work right.  Doing this requires some major readjustment and knowledge of panel configuration.  But it is possible with a little help from the folks here . . .