Front and rear diff??
For the front, use the drain plug at the front of the transmission. It is a 21 or 22 mm head. Then add new through the top like the ATF but on the passenger side.
For the rear, there are two plugs that a 1/2" breaker bar will fit into. The bottom one is the drain, the top one is the fill. MAKE SURE THAT THE TOP ONE CAN BE REMOVED BEFORE YOU DRAIN WITH THE BOTTOM. Otherwise you will drian it and only be able to fill to the level of the bottom hole.
edit: Damn, you beat me, but at least I got the size of the Front drain plug right 
