Done. Now your server will be fully backup to a remote FTP server and all files, older than N days will be deleted.
I prefere numbered-backups instead of adding the date to each backup.
Instead of server01-files-$NOW.tar.gz i use something like server01-files-$DOY.tar.gz
DOY=`expr $DOY1 % 10` # for 10 Backups (0..9).
No need to delete old files, they are just overwritten.