Could a PPL fly a 747? was the orignal question. I think it was a question about it being possible, both logisticly and legally. We've suffered a bit of thread creep, we are now on 'could a 747 be landed if the pilots were incapacitated?' I think both questions have been answered.
If you're talking about a PPL sitting on the flightdeck and thinking he will click the autopilot out and have a go, it will likely end in disaster. From being in the cruise and finding an airport where he can get the thing in a position to land it manually will be so far removed from his experience that he wouldn't be able to cope - let alone the landing. The sceanrio where my son got it on the ground is very very different. He was just sitting there pushing the buttons on my instruction. It was actully me flying the thing while not looking at what he was seeing, just looking at a plan of the flightdeck to remind me where things were, as although I'm rated on the 744, it's 4 years since I last flew it. He had little understanding of what was going on, he was just reporting what he could see. The first thing I would have said was "Don't touch the control column or the thrust levers - at all!" The scenario where he would have diconnected the autopilot would have been a disaster. In this case a lack of knowledge was beneficial.
The 744 is designed to be flown on automatics. If you were the 30 hour pilot and got on the flight deck in the cruise, you will find it on autopilot. Picking up the hand mic and just talking would get a response, even in half way across the Atlantic. Being talked through the rest of the flight is plausible, even if the approach wasn't loaded. When you set up for an approach, it defaults to a CAT3 ILS, you actually have to intervene to do otherwise. (Most 744 pilots leave the automatics in until the last moment anyway. On long flights getting back into Heathrow at 7am, I was knackered. The autopilot wasn't disconnected until 200' usually).
And a manual landing? The 744 is actaully very easy to land - there is an auto rad alt call up. At the 50' call, you just start to close the thrust levers, at 30' you selct 2 degrees nose up. You don't have to kick off any drift because when the body gear touches down, the fusleage gets lined up with the runway (Boeing recommend not kicking off the drift on wet or contaminated runways anyway). And forgetting to flare? Well, if you do a real CAT3b autoland and you don't get the flare mode, you can't click out the autopilot and flare it manually because you can't see the runway at this stage. The procedure is to let it land without flaring, but Mr Boeing says this is OK and within normal limits anyway! Getting it to the stage where it could be landed would be the difficult part.
The Classic is harder to land BTW. It has to be flown all the way down to the ground.