Answer: Unless your delay will cause you a loss there is certainly a moral obligation to help someone by showing him how to get to where he wants to go. The reward for such a slight service is evident from what is described in Shoftim 1:24-26.
The Tribe of Yosef encountered difficulty in discovering the carefully concealed entrance to the city of Beit El, which they wished to conquer. When they saw someone leaving the city they asked him to reveal the entrance. All he did was point a finger to the entrance, which enabled the Yosefites to conquer the city. He, together with his family, were spared and they founded a city called Luz which survived all the invasions of foreign armies.
If this is the reward for a mere pointing of the finger, how much greater will be the reward for taking the time to give directions.