2002 Yukon 4x4 front axle leaking
 

I have a 2002 Yukon 4x4 and the front axle started leaking about 2 weeks ago. I thought it was the drain plug, because it seemed loose. After tightening the plug, refilling the case, and cleaning up, it is still leaking. I think it is leaking around the seal. What is the process of replacing this seal?

Thanks