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?"
