How to 'watch' my Linux Server for changes done in files

Hi,

Recently one of the key config file of my application running on Linux box was changed by some user 'accidentally".
 
I would like to know how can I watch my server and log changes being made to specific folder or files. What time the change was made, which user made it etc.

I looked at auditd but it looks so confusing.

Any idea about any other possible solution? If there is a central logging for all my server "changes" it will be even better!

Thanks and Regards,
Amit Sharma