Ok... (I wish you had ICQ, or something, so I could talk to you one on one for this, but...)
To make a piece of geometry destroyable is simple. Remember how we made the turrets? Well, it's essentially the same for the subobject in question. Create the piece of geometry, attach it to the main hull as you would a turret, and convert to pof form.
Now, in PCS, you'll go to the subobject section, and for that object, add:
$Special=subsystem
$name=door (Or whatever)
and save the model. Then you can go into the table file, and set the part of the geometry as a sybsystem. Make sure that you name it correctly, after the name of the subobject, and not the $name part.
Does that make sense?
Edit: If you wanted to get real fancy, and add a destroyed lump, or live debris for it, you could either make the destroyed door mesh, position it correctly, and add -destroyed to the end of the name. (I.e: if the door was named hangerdoor, the destroyed part would be hangerdoor-destroyed. The same works with turrets.)
You could also make multiple pieces of debris, IIRC, the same way, but instead of -destroyed, you make it -debrisNN, where NN is 01, 02, 03, etc... And the pieces should float off into space.
But I may be wrong on that, since I've never tried it/got it to work correctly.