Numpty!
Anyway, I have some pics of my tranny when I was converting it to single speed- both the cheap version and full version. Take a look on my website for pics, should give you some idea of what to do:
http://www.robotwars.00server.com/txtproject.html
Pretend the coupler (silver thing) is the drive dog, and it is bolted/glued to the 2nd gear output gear in the same place. Then just remove the 1st gear idler (leave the shaft there though), and trim down the 1st gear output gear so that just the center is left to act as a spacer on the output shaft.