Can easily be done with PCS2 w/o Blender.
Open the Hecate model.
Go to SubObjects (left).
Then click the "load" button on the upper right.
Select the Titan model.
PCS will then show you a list of all Objects (LODs, Debris, Turrets etc) - click on the one you want to have.
You may want to rotate the turret in case it is not exactly matching the hull. For that, stay on SubObjects, select only the turret, go to the other button Transform, which allows rotating around axes, resize and different centerpoints.
Zooming - in and out - to check whether everythings' OK can be done with scroll wheel on the mouse.