An interesting idea, can an armchair pilot land an airliner? There should be no problem.
As long as the new pilot has the calmness to remain in control of his emotions, and the situation, there should not be a problem with him/her controlling a modern airliner to an uneventful landing.
The trick is for him (I'll risk being non-PC by refering to the hero as a male!!) to communicate the predicament, and to keep the AP in. If he can do that, and be talked down, there would be a chance of success.
Having said the above, please remember that I said " a modern Airliner" There are many aircraft being flown about that do not have Autoland capability. If that is the case, then all bets are off. The ability to handfly a B737/DC-9 or bigger aircraft is not something that can be taught on a PC simulator.
From another angle, if I was to talk a non-airline pilot down, I'd rather take a private pilot over a PC pilot, and if the AC is modern, with full automation, I'd rather have a complete novice there, who will not question or second guess me, because his MS FS2000 doesnot have feature "x" that my company's AC has fitted! Sometimes a little knowledge can be dangerous.
Remember, if something like that were to happen while you are on-board, there is a chain of command, and PC pilots are not mentioned anywhere in that. Your most likely involvement would be to operate a radio while an off-duty pilot jumps in to drive, or a cabin attendant makes the MCP selections.
Still, there is nothing wrong with thinking through a possible scenario, it may come in handy one day (or the storyline of a novel) Just remember, if it does happen to you, manage the risk by keeping the AP engaged as long as possible. It will free up your brain power to concentrate on what you are being told/asked by the outside people.
If you get the urge to hand fly, just remember that even experienced airliner pilots normally do 40-90 hours in a full-flight simulator before they fly a new aircraft for the first time. You can only enjoy being a hero if you (and all those behind you) survive.