What made your friend think that air traffic controllers would be able to give instructions on how to land an aircraft?
(As a rule of thumb, they don't. And even most pilots couldn't help, only pilots who know the aircraft in question and if auto land is an option at all.)
You can keep a plane flying straight and level while they go and find out. They know that there's a plane in distress and can route traffic around it, and get someone on the horn.
Sure, it would be unusual for a random individual controller to be able to give instruction on landing a 747.
But I can guarantee you that they would arrange for someone who did to help you. For immediate help, there would likely be another pilot in the sector that that controller could ask to help keep you in the air. While that is happening, other controllers or supervisors would be calling the airline to get a type-certified pilot/instructor on the radio to talk you through the landing.
I don't know of any cases where it has actually happened on a commercial, but there have definitely been cases in light aircraft where the pilot became incapacitated and ATC talked the non-pilot through a safe landing.
It's still the right thing to do to contact them and ask for advice, they have emergency services to arrange, traffic to clear, and many have flight experience of some kind or another. More to the point they are at the twitching heart of the airport and can get on the phone or handball the task of patching through to a pilot that does have the relevant experience.
Even small airports have a surprising breadth and depth of experience hanging about the associated flight schools and maintenance sheds, the chances of finding a semi retired 747 (say) pilot lurking about with the older mechanics working on a light aircraft or custom built car are surprisingly high.
An ATC will be able to help by quickly getting someone who can help on the phone or in the tower. Finding someone with knowledge of the particular aircraft in question is seldom a problem, especially not at an airport.
Your very optimistic. There's no standard procedure for this kind of emergency. Sure, ATC will try to get help, however, depending on the type of aircraft, it might not be possible to fetch a pilot or another expert to due a talk down on time. For a common aircraft type it might be possible, for others, well …
You're most likely to encounter a common aircraft type. Airline sompanies have reserve pilots that they can call on short notice, so it's highly unlikely that ATC will be unable to find someone to help. If you're in a small plane, there are many flying clubs they can call. All of this in the case that there are no pilots available on the current airport.
See this video for an example of an SEP pilot landing a King Air:
Manufacturers of large airplanes maintain emergency contact numbers that you can call when one of theirs is in trouble and you need their help. Typically, calls involve things like: "I'm looking at the plane on the ground, x looks like it has broken off, what do I do?" instead of asking for instructions to land the plane, but I can assure you that they can give that kind of advice on short notice too.
> "I'm looking at the plane on the ground, x looks like it has broken off, what do I do?"
Having sat in an airplane seat for two hours while this exact thing happened, I sure hope their response times are faster if the question is "The pilots are dead, how do we land the plane?"
(As a rule of thumb, they don't. And even most pilots couldn't help, only pilots who know the aircraft in question and if auto land is an option at all.)