No editing :(
http://spacemods.googlepages.com/Client_MissionEditor.zip if it won't work. Place in your Addons folder.
That tutorial is shunned, but the other link there might help. (
http://forum.blockland.us/index.php?topic=91400.0)
My tips (Made quite a few maps in torque games) are to make sure the terrain is smooth, but not creamy. You have to have sharp points. Also make (or steal unknown terrains) terrains around 512x512 in size and to have few laggy effects (FX light / suns, rapidly moving water, moving skies at a faster rate, long view distance, lots of fog) as they usually slow down your map a lot.
Try to make your map original. No damned flat maps, unless they have very unique enjoyable atmospheres.
You can also look into model/interior makers, like the
Torque Constructor.
All in all, practice, practice, practice. Also, don't release your first map unless you know it's good. And try to avoid stealing other people's works as there would usually be conflict. Good luck.