Looks like you’re dealing with a pretty tricky issue there! It’s definitely frustrating when you just want to tweak your settings but keep running into those authentication errors.

First off, yeah, those “token manipulation” errors can be a head-scratcher. It often points to something going wrong with authentication, and it could relate to file permissions or your PAM settings, like you mentioned. Here are a few steps to try and hopefully help clear things up:

1. Check Your System Logs:

   Open a terminal and run:

   sudo less /var/log/auth.log

   This might give you more insight into what’s failing. Look for lines that show up when you try to change your settings.

2. Check your password expiry:

   It’s possible your password has expired. Run this in the terminal:

   sudo chage -l your_username

   Replace your_username with your actual username. If your password is expired, you’ll need to change it with:

   sudo passwd your_username

3. Look at your home directory permissions:

   Wrong permissions can cause issues, so check them with:

   ls -ld ~

   You should see something like drwx------. If it looks different, it might need fixing. You can update permissions with:

   chmod 700 ~

4. Reinstall `login` package:

   Sometimes, reinstalling certain packages can help. Try running:

   sudo apt-get install --reinstall login

And, yeah, if you’re using an older version of Ubuntu, you might want to consider updating if possible. Sometimes updates can fix underlying issues.

If you mess something up, don’t worry—you can usually recover from most changes, and also having a backup is always a good practice. But make sure to follow these steps carefully, and hopefully, you’ll be back to setting things up for your project in no time!

Good luck, and hang in there; you’re doing great learning this stuff!