Replace line in text file with user input at terminal

I am trying to prompt the user for two pieces of information:

1) The line number in the file to be changed 2) The value to change it to.

My script so far:

echo "Do you wish to enter a variable to be changed?"
select yn in "Yes" "No"; do
  case $yn in
    Yes)
      echo "Please enter a variable to be changed"
      read lineNum
      echo "Please enter variable's new value"
      read val
      awk -v lineNum="$lineNum" -v val="$val" \
       'BEGIN { if (NR == lineNum) print val; else print $0}' \
        test.in > newtest.in
      ;;
    No)
      break;;
  esac
done

The test.in has numeric values all in one column:

1
2
3
4
5
6
7

Thanks.

EDIT Forgot to mention the error :D. For some reason, the a new file is created but only with the new val that was specified, I imagine this might have something to do with using $0, but I haven't been able to figure out how to fix it.