My program is supposed to read in a file and a word from the user then replace every instance of the word inside the program with another word entered in by the user. I keep getting function errors and cant get past the compiling process

Here is my code:
#include <iostream>
#include <fstream>
#include <cstring>
using namespace std;

int main()
//Varibles needed to make sure that the program will run effectively
fstream dataFile;
char *buffer;
string find, change;
int count = 0;
int length;

//Opening the data file to be a input and output (Read and Write)"input.txt", ios::in|ios:ut);

//Testing to make the file opened
if (!dataFile)
cout << "File open error!" << endl;
return 0;
//Getting the length of the file
dataFile.seekg (0, ios::end);
length = dataFile.tellg();
dataFile.seekg (0, ios::beg);

//allocating memory for the file
buffer = new char [length];

//Read the buffer into the file

//Asking the user what word would they like to search for
cout << "What word do you want to search for?" << endl;
cin >> find;

//Asking the user what word they want to use to replace
cout << "What word do you want to replace the first word with?" << endl;
cin >> change;

while (!dataFile.eof())
do {
if (strstr(find,*buffer) == 0)
} while (!dataFile.eof());

dataFile.replace (buffer, find, change);

cout << buffer;
return 0;