cant find the proper procedure for trans. service !!!

I'm having trouble trying to find the proper way to service the transmission on my 2010 lgt ... on Monday I'm buying 5gal. Bucket of extra s from the dealer and would like to know how to drain the trans and center diff? When filling threw the dip stick tube does the fluid over flow the center diff to the trans??? .... trans take 4.1 and the center diff takes 1.3 or so? Some one please explain this to me please??? Thanks

The center differential is a viscous unit and is inside the transmission case and is sealed - it is not filled on it's own. The transmission take 3.9qts and the rear differential takes 0.8qts.