theme change

I’d like to modify code to have the option of sidebar or no sidebar on individual blog posts. I found the code to do so in a wordpress book which, if it works as advertised, gives you a check box for sidebar or no sidebar on each blog post. Has anyone had experience with this? It involves changing the single.php and the loop.php file. I’d like to know if there are any unstated pitfalls in trying this. Will have multiple backups before attempting.