Welcome to LQ!
I'd like to start with a suggestion to instead give Postfix a try as an excellent drop in replacement for Sendmail. It's much more newbie friendly, more secure, works out of the box on most setups, and is just as powerful (arguably more). That said...
Where did you create your sendmail.cf file? What I'm guessing happened is that you already had a file with the same name in that directory, and when you wrote the file, it overwrote the current (working) one. You have a few options now, you can play with a new sendmail.cf file, getting all the options you need worked out, and [probably] eventually getting it back up and working; or
You can uninstall the sendmail rpm:
rpm -e sendmail
And then reinstall the packages that get removed, this should refresh those files that you have tweaked/removed. Be sure to backup anything that you have customized and know works if you choose this option.
Also... Maybe when you deleted the file, you didn't restart Sendmail so it would re-read the older/working conf file?