If you do not want to involve your PC at all, you will need to invest in a small unit called a NAS.. (Synology, Q-Nap, Netgear, Drobo, etc.). Some of them can get pretty pricey. If you only need 3TB worth of data (one hard drive worth) you can buy a single bay NAS for one hard drive. This will not help with your external hard drive tho (You could always open it up and use the hard drive located inside of it if you wanted to do that).
The problem is your Samsung TV or Xbox is going to need something to "feed" the media files to it. Your external hard drive alone does not include the needed software to feed the files. It can STORE the files..but the DLNA on your Samsung TV needs to communicate with a piece of software to say "ok here you go TV here is the media files you're requesting". I would not suggest building your own NAS server if you're not technically sound.
There are many ways and setups you can do this. You can go with a cheaper route or you can go with a pricer route that may be more visually pleasing in the experience.
Here is a link to a 2-Bay (can hold up to 2 internal hard drives) NAS that is pretty affordable, allows expansion, and it works really well: http://www.newegg.com/Product/Product.aspx?Item=N82E16822108095
Keep in mind the above price does NOT include any hard drives. It's also fairly easy to set up for even a novice.. It may look scary but there is a guide that will walk you through the whole process. If you do in fact use such a device it is capable of feeding your media files to your TV WITHOUT having to involve your PC at all.. The NAS units use a very minimal amount of power and they operate fairly quietly.
You would connect the NAS via ethernet cable to your router and once setup your TV should be able to "see" the NAS unit with all of your media files located on it.
You also have the option of running free software (I suggest Plex Media Server) on your PC...and connecting your current external hard drive to your PC and use that as storage for your media files. Your Samsung TV would then connect to your PC via ethernet cable (wireless is not good for streaming movies in most cases) and your PC would serve the files. This would be the lowest cost option for you with the equipment you have...but obviously it would involve your PC use.
I tried to explain all of this as simply as I can...hope it helps