Yes, you would have to pay 1 SO point for attacking the one in the German Transit area, and 2 SO points for attacking the unit in the German Staging area. The one in the Front won't cost anything.
There is an example of what you're talking about on Page 21 in the Sample Game. He has the game setup as 3A is in THE FRONT, and 6A is in the German Staging area. The game sample says:
With that in mind, I attack: 3A "in the Front" (1 point) and 6C "in the German Staging area" (5points). Normally, it would cost 1 SO point to Attack 6C
because 3A is in the German Staging Range Band, but I assign
my Truck to the 6C Battle. The Truck reduces my SO point
cost by 2, so I don’t need to pay any SO points.
I added the parts BOLDED in Quotes and Italicized.
Hope this helped!