I did the trolley/taxi for my fill but I came from the train station, not the airport. It's really easy. I was a bit nervous since my train was late and I didn't arrive at the border till almost midnight and I was by myself. Looking back, there was nothing to worry about. Getting back across the border took me about 30 minutes (on a Monday morning). There are lots of cabs near the border that will take you across for $5 and apparently they use a special lane and you will be across within 5 minutes. I chose to wait since I had time to waste until my train left.
Hope this helps