Adding an update node into a linked list - c

Question

I'm having trouble figuring out how to do a update function in this current code. He does not want us to change the student ID, but wants us to change the GPA and the major associated with the current student. He wants us to
create a prompt for the user to enter the student ID number to search for. Also to create a prompt to determine which field the user wished to update then accept new input for that field and change the contents of the appropriate student. I don't want the answer. I just need to be pointed in the right direction.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "stuff.h"
#include "staticll.h"
int compareID(void*, void*);
int compareGPA(void*, void*);
int compareMajor(void*, void*);
void main(void)
{
FILE *fp;
struct Node List[15];
int Begin, current, newStuff, oldStuff;
double oldData;
int(*fnPtr)();
fnPtr = compareMajor;
Begin = 0;
struct Student *stu;
for (int x = 0; x < 3; x++)
{
newStuff = FindSpace(List);
List[newStuff].nodeData = readData(stdin);
addNode(Begin, List, newStuff);
}
for (int i = Begin; i != -1; i = List[i].nodeLink)
fprintf(stdout,"%.2f\n",((Stu*)List[i].nodeData));
for (int i = Begin; i != -1; i = List[i].nodeLink)
free(List[i].nodeData);
}
int compareID(void *p1, void *p2)
{
if (((Stu*)p1)->stuID == ((Stu*)p2)->stuID)
return 0;
else
if ((((Stu*)p1)->stuID < ((Stu*)p2)->stuID))
return 1;
else
return -1;
}
int compareGPA(void *p1, void *p2)
{
if (((Stu*)p1)->stuGPA == ((Stu*)p2)->stuGPA)
return 0;
else
if ((((Stu*)p1)->stuGPA < ((Stu*)p2)->stuGPA))
return 1;
else
return -1;
}
int compareMajor(void *p1, void *p2)
{
return strcmp(((Stu*)p1)->stuMajor, ((Stu*)p2)->stuMajor);
}
This is the current code I've created for the update function needed.
#include"Stuff.h"
void updateNode(struct Node List[], int current, int *NewData)
{
int temp1;
List[current].nodeLink = List[*NewData].nodeData;
List[*NewData].nodeLink = NewData;
printf("enter the student ID number ");
}