What was found
FLIGHT 3117 - BUF-LGA - SHORTLY AFTER TAKEOFF, EICAS MESSAGE "LG AIR/GND FAIL" APPEARED. REQUESTED "GEAR UP" AND FO TRIED TO SELECT GEAR HANDLE TO UP POSITION, WOULD NOT MOVE. DECIDED TO CONTINUE CLIMB AND DIAGNOSE THE PROBLEM AT A HIGHER ALTITUDE. RAN QRH. DECLARED EMERGENCY. AFTER LANDING, RECEIVED "IC 1-2 WOW INOP" AND "SPS ADVANCED". REMOVED AND REPLACED LGEU.