This topic reappears every few years, the outcome is always the same with som PPL guy confident in his ability to save 450 pax in a 744 and the airline pilots saying that it is more likely to end up in a fireball.
The longest of these discussin was about 8 years ago and I seem to remember the final conclusion was that if the PPL keeps the autopilot in and follows instructions very carefully, then there's a chance. The overconfident one may decided to try his luck and disconnect, find he can't do it, try to re-engage the automatics and then get it wrong having put themself in a worse position. As an experiment, from this discussion, I put my (then) 11 year old son in front of a PC sim we used to use for 744 training and talked him through an apporach and landing from the cruise. He could do it - but it was a PC sim without the distractions of being in real cockpit.
I have had experience of putting non airline pilots in a sim for them to have a go. My experience is that most, after a couple of attempts can land it (with the crash inhibit on!). This can be resolved on the first approach by leaving the autoland in. As most airliners defualt to autoland anyway, there should be no problem, but if there is, driving it in at 7-800' a minute won't do much damage as the airframes have been designed to cope with this. The problem these guys have is getting it into the situation where a reasonably stable approach can be made. They generally don't have the experience or skill to slow it down and get it into a position, being configured on finals to do the job.
As for the sims available for public use, there's two 737 sims near where I live and they are rum by PCs and don't have motion. I've used them on a few occasions - thye are impressive for what they are, but nothing more than a toy. They won't give handling feed back and not having flown the 737, I can't comment on their accuracy, but I suspect they are close, but as they aren't certified for pilot training, not close enough.