After taking a second look, I just realized you started the thread I posted above to try to help out. Sorry, didn't put 2 & 2 together until now. Doc explains there why the H3 doesn't have the radiator drain plug though and how to change the coolant.
Hope your thread helps... lol
2007 Hummer H3 (ADV)
2007 Uяal Gear-Up
2009 Royal Enfield Bullet 500avl