You are correct.
しばらく for a while、経<た>った It(Time) passed ※経つ to pass(about time)、頃<ころ> time
When it passed for a while since the situation cooled down=a short while after the situation cooled down
事件のほとぼりが冷めてしばらく経った頃
When the public excitement of the case cooled down and passed for a while