That's not quite accurate. The XBox 360 does not run DirectX 10, but runs a highly modified version of DirectX 9. It is not a straight port. Unless TGC wants to port it to the 360, and you are all willing to eat the cost of a developers license for the 360 (to clarify, everyone who intends to develop for the 360 would need a dev license. This is well over ten grand each.), you won't be the GDK for developing 360 games.
That all said, if you DO what to write games for the 360 you should look into XNA. It's not very complicated and there is plenty of material on how to use the system, including a great number of starter projects.
-Piro