Has Air Traffic Control ever had to talk a first time pilot through a landing due to an emergency?
The answer is yes.  One example was on April 2, 2012.  Helen Collins, an 80-year old Grandmother was forced to take the controls of her husband's CE-414 and land it at Door Country Cherryland Airport (KSUE) after her husband had a massive heart attack at the controls and died.  She managed to circle the airfield and call 911 on a cell phone.  The emergency dispatcher contacted the FAA who got in touch with ATC.  A KSUE based private pilot named Robert Yuksonavich took off and joined her in formation, talking her through what was about to happen and flew her wing on several practice approaches prior to the landing attempt.  On landing the Cessna 414 skidded off the runway and came to a stop in the grass, breaking the nose gear off.  Helen survived with only minor injuries; her husband was pronounced dead on the scene.

A brief piece by the CBS morning news featuring commentary by Capt Chesly Sullenberger about the incident.


                
            

This is the full ATC of the accident