From what I can see, uPnP/dlna will work. No additional hardware required.
You can upgrade to FreeNAS 8.0.4 "multimedia" very easily. Just remember to back up your config to be safe. This version comes with minidlna but there is no gui for minidlna so your setup will need to be done from the cli but it's basically just entering the location of your media directories. This thread will help
http://forums.freenas.org/showthrea...dlna-on-the-freenas-nightlies-post-09-25-2011
I personally would stay with 8.0.4 until 8.2 is released and the jails have been fully tested. The changes between beta 2 and beta 3 were substantial. To answer your question, yes you will need to upgrade, but you are effectively staying with the same version of FreeNAS, just adding minidlna support. Your current setup will remain.