When changing mine, I have used Lucas Hub Oil - Stop leak. Many of the Hummer guys recommended it for small leaks on the H1's. I had success on my H1 and gave it a try. It seems to work well on my M998 as well.
Be careful with the hub drain plugs. It does not take much to spin the Allen head. I used a bit of heat before pulling mine the first time. Then, reinstall only to spec torque. It is a lot less than you think doing it by hand.
BlueHummer sells an extraction tool and replacement plugs. I recommend having both on had when you do the hub oil change.
Best of Luck.
-Economist.