Copy Constructors and Assignment Operator, When should I use?

Hi, all:

I know this is a basic concept but I still need some clearification.
It gave me a hard time

I read something says "Don't write a copy constructor if shallow
copies are ok" and "If you need a copy constructor, you also need a
destructor and operator="

My understanding, the shallow copy work for class that with int,
float ...etc internal datatype only. If I have pointers or vectors, is
that means I need to write my Copy Constructor/Operation operator.

Nothing clearer than an example.
Let's say I have a class:

Class ItemSet{

      ItemListA a;
      ItemListB b;

load() // call ItemListA.load(), call ItemListB.load()

}

Class ItemListA{

struct ItemA{
    int aInt;
    std::string aString;
} ;

std::vector <ItemA> m_vecA;

void load(); //function for populate m_vecA
ItemA FindItem(){
   ItemA ia;

   return ia
}

}

Class ItemListB{

struct ItemB{
    int bInt;
    std::string bString;
                time_t: bTime;

} ;

std::vector <ItemB> m_vecB;

load(); //function for populate m_vecB
}

----------------------------------
Now Can I do:

ItemSet set1;
set1.Load();

ItemSet set2;
set2 = set1

? without create copy constructors for ItemSet class?

If I need to create copy constructor for ItemSet class, since
ItemListA and ItemListB is in ItemSet, I also need to create copy
constructor for these 2 classes, right/

-----------------------------

Also, if I need to create the copy constructor /overwrite assignment
operator for Item:
why does the function in ItemListA which returns struct ItemA work? Is
the return COPY the ItemA ?

Thanks a lot
-rockdale