My program should read five integers from a file called sample.txt, then print out the integers, add them, etc. using the overload functions. I seem to be having a problem with my isElement, insert and remove functions, but I'm not a strong coder so I just can't figure this out!! Here is my code, then my 3 errors follow. Any help you can give is appreciated!!

Code:
#include<iostream.h>
#include<fstream.h>

struct Node{
	char digit;
	Node *next;
};

class BigInt{
	Node *Num;
	int cap;
	int top;
public:

	void insert ( int);
	void remove (int);
	int isEmpty () {return !top;};
	int isElement (int);
	int size() {return top;};
	friend BigInt operator+(BigInt A, BigInt B);
	friend BigInt operator-(BigInt A, BigInt B);
	friend istream& operator>>(istream& in, BigInt &B);
	friend ostream& operator<<(ostream& o, BigInt &B);
};

int BigInt::isElement (int target)
{
	for (int i=0; i < top; i++)
		if (Num [i] == target)  //ERROR 1
			return 1;

		return 0;
}

void BigInt::insert (int target)
{
	if (isElement(target))
		return;

	if (top == cap) {
		Node *temp = new Node [cap + 5];
		for (int i=0; i<top; i++) temp [i] = Num->next [i];
		cap =+5;
		delete []Num->next;
		Num->next = temp;
	}
	Num->next [top++] = Num.target; //ERROR 2
}

void BigInt::remove (int target)
{
	char i;

	if (! isElement (target))
		return;

	for (i = 0; i < cap; i ++)
		if (Num[i] == target) //ERROR 3
			break;

		while (i < cap -1){
			Num [i] = Num [i+1];
			i++;
		}
		top --;
}

BigInt operator+(BigInt A, BigInt B)
{
    A.Num->digit += B.Num->digit;
    return A;
}

BigInt operator-(BigInt A, BigInt B)
{
    A.Num->digit -= B.Num->digit;
    return A;
}

istream& operator>>(istream& in, BigInt &B)
{
	in >> B.Num->digit;
	return in;
}

ostream& operator<<(ostream& o, BigInt &B)
{
	o << B.Num->digit;
	return o;
}



void main()
{
	BigInt v1, v2, v3, v4, v5;

	ifstream in;

	in.open("sample.txt");

	in >> v1 >> v2 >> v3 >> v4 >> v5;

	cout << v1+v2 << endl;
	cout << v3-v4 << endl;
}
errors (line location shown in code above):

1. binary '==' : 'struct Node' does not define this operator or a conversion to a type acceptable to the predefined operator

2. left of '.target' must have class/struct/union type

3. binary '==' : 'struct Node' does not define this operator or a conversion to a type acceptable to the predefined operator

Thanks!!