A normal is vector associated with a turret - the turret will fire along the normal. A turret's field of view is given as a cone centered over that normal. And so forth. The important thing to remember is that the normals for mulit part turrets must point straight up or down, or they won't work properly.
Which version of PCS are you using? Some older versions have major issues, but I'm using 1.3.4 and it works perfectly.
I much prefer using ModelView when I can (you need version 1.0Beta 04b build 26 for the POF editing facilities), but it can't do all the things that PCS can do. Using both in conjunction is the best compromise.
Another editor is Boboau's Aurora. Check his sig for details.
Otherwise, whenever you have quesiotns about modding, always check karajorma's
FAQ first. It will help to answer 95% of your questions
