# yum install vsftpd
# service vsftpd start
# chkconfig vsftpd on
The config file is at /etc/vsftpd/vsftpd.conf , which you should change according to what you want to do. The config file has lots of comments and there's excellent documentation at the vsftpd site too: http://vsftpd.beasts.org/
2) Ummm, what? sendmail is for SMTP, FTP is for FTP. They're completely unrelated protocols.
3) The sources are available on the vsftpd site, but I have no idea what it is you're wanting to do.