You shouldn't have to specify the version, if YUM is any good you'll just be able to type yum install mozilla (or yum upgrade(?) mozilla if it's already instead) and it'll automatically download and install the latest version. You may have to synchronise your local package database against an online database before you'll get the latest packages but I don't know how to go about doing that (now, if it were Debian or Gentoo...) or even if it's necessary.