Virtual Cockpits are a bit more complex than the exterior of the aircraft. to make a good VC, you will have to make many more tiny animated switches, and the texturing is an art itself.
other than that, I do not know of a way you can combine a different VC to an existing model?
My advice to you is to first start modelling the exterior, and learn the way Gmax, exporting to MDL, etc work, before commencing a complex VC. There are several tutorials on the web regarding VC's. The two sites I can reccomend you browse is http://www.aerodynamika.com/ and http://www.fsdeveloper.com/forum/index.php

Enjoy