RE: How to change transfer case fluid
The fill and drain plug have a slot to insert a 10mm hex wrench. Since the plugs are rounded, this is the best way to remove them so you don't risk damaging the threads trying to use plyers or channellocks on the plugs. I use Dexron III in my transfer case becasue that's what my manual called for, but I think ATF + types work ok too. The standard 231 transfer case common on most of our trucks holds 1.5 qts, as does the less common 231HD. But, it is unlikely you will be able to get more then about 1-1.25 qts to actually come out unless you try jacking up the front of the truck at the same time your draining. If you happen to have the 241 (some 2500 and 3500 models have it), it holds almost 2.5 qts.
You will need a squeeze bottle (or squeeze bottle tip to put on your regular quart bottle) to put the new fluid in since the fill plug is up so close to the underside of the truck, there is vertually no room to tip a standard bottle, and no room for a funnel. I like to buy a couple of quarts. I let the case drain, then I squirt in about 1-2 qts until it is running out the drain clean. Then I close the drain and fill it with new fluid.