I was just kidding about the prize.

Seriously though, AFCAD is super easy to use. I can give you the steps right now.
1.Start AFCAD
2.File/Open Aiport
3.Enter airport ID in search box and click search
4.You'll see the stock airport listed, click OK
5. Now you'll see your airport, right click on the runway and choose properties
6.Under Runway Data you'll see length and width, change them to the values you want and click ok
7.Hit File and Save As, it will save as a mod file and will not change the default airport file. If you want to return to the default setup, the mod file is simply removed. The mod file is a .bgl file which begins with AF2_ and lives here: C:\Program Files\Microsoft Games\Flight Simulator 9\Addon Scenery\scenery