You can do a lot with Adobe Photoshop CS4 or CS5 editing software, but using the "after effects" module you can do some amazing editing. Including cloning foliage or text, frame by frame over existing footage of an old video.
Here are a few videos to show how easy it is to do...
Also, why no sound. I think because it was to hard to edit. That one scene where there was nothing but video from a mile away and then a newspaper shows up in full screen, seemed kind of suspicious to me as if it was cut and pasted in. There would be a gap in the background sound on the video. You should at least hear wind or gravel under foot as he walks around. The person filming or equipment noise in the background. But nothing. Did they rush it through to get it posted and not have time or what?
Imo, it's just one more attempt to scam SRGE shareholders. BGL has already been proven to fabricate what ever they need to perpetuate a lie.