Thanks to colincliff2 for the most important part: ATF quantity.
This is only
to change the trans sump fluid out (not a complete system fluid flush/refresh)
Optional: warm car up, but if you do, wait for cats to cool before proceding and be careful of hot fluid! -- I do all of my vehicles cold -- and if you feel like you have to comment on that, just do yours warm or hot...
Park on level ground, or with the front passenger side raised slightly (pan's drain plug is rear drivers side).
I rolled my J up on 2x6s to get clearance to get under the car and achieve the above (1 under each tire and 2 under front passenger tire) -- this is if you are on a pretty level surface...
you'll need: most important!!
: a long neck funnel to put new fluid in the trans dip-stick tube (under hood passenger side -- look at manual if not sure where) Be Sure To Check That Your Funnel Fits In The Tube Before Proceding!
drain pan, latex gloves, clean rags or paper towels, 3/4" or 19mm socket (preferably 6 point) and ratchet, 2 - 2 1/2 qts Dexron III (or an equal to it in synthetic ATF).
Once more: make sure your funnel fits in the dang dipstick tube!
Slide under car with your ratchet set to counter-clockwise rotation and your handy drain pan -- have a rag with you. Look for the rectangular pan in middle/front of driver's seat area under car and just break lose the 19mm plug (to finger tight) that's at the rear drivers side corner of the pan. Be careful here, as the hex head on the plug is shallow and easy to strip the corners if you have the socket tilted at all
Slide your drain pan under and unscrew the plug by hand. If you are just up on 2x6s like me, there's not much room so this is sort of done blind. Clean your hand that is now covered in ATF...
Let it drain until just a drip every several seconds or so is coming out. Clean plug area and plug -- take a look at the plug gasket (rubber washer) for cracks, etc., otherwise it's reuseable for many times. Put plug in and tighten -- do not reef on your ratchet or your WILL strip the plug threads -- just make it's good and snug, like you'd tighten your oil drain plug. If you've never changed oil an a car, you shouldn't be doing this either!
Get all your stuff out from under the car and it's a good time to take a look at the old fluid -- I dip a corner of a white paper towel in it and look at the color and smell it as well. If it is a nice pinkish red color and smells sort of sweet (open a bottle of the new ATF and compare color and smell), You are in good shape and don't need to do this often.
If the color is reddish brown, brown or
black and smells burnt at all... Well let's just hope it's the reddish brown at worst and proceed, if it's darker I suggest you get a full fluid replacement/flush done and get some religion...
Make sure your funnel is nice and clean and clean around the area of your trans dipstick (not just the dipstick itself) before you pull the dipstick out. Pull the dipstick, wipe it off and put it in a clean area on towels, etc. Stick your funnel in and hold it in place while you put in 2 qts of new fluid (thanks again colincliff2). If it's winter and/or you don't drive in hot or hilly areas, or a lot of stop and go, you can go up to 2 1/2 qts. But I'd start with 2 and check it and then add the extra fluid if you decide to -- the dipstick will read in the high area if you go all the way to 2 1/2 though. Take a peak under the car to make sure the plug isn't leaking.
Put your dip-stick back in (fully) and drop the hood and start the car. With the brakes on, run the trans shifter through each gear -- not all that necessary, but just in case to be sure the trans hydraulics are fully packed.
Take a short drive and check the fluid level per the manual (hot check) and add fluid if necessary.
If your old fluid was not quite red, maybe getting a bit on the brownish side, I'd do this drain and fill a number of times over the next couple thousand miles until the fluid is fresh looking/smelling. As a reference your total transmission system capacity from bone dry is 8.75 qts.