Hi,
I have done the fluid / filter change a couple of times on my '96 3.8L.
Your 2000 will be similar. You will use Mercon V rated fluid....with is different from the Mercon fluid that I use.
Verify which tube is the return line for your 2000.
The other place that fluid (old and new) can mix is in the torque converter. I posted pictures that show what you will be seeing.
What I did is to disconnect the return line from the cooler.....slide a short piece of clear hose over the cooler return hose.....so that I could easily see the fluid flow.
I ran the engine until the fluid flow pretty much stopped. I measured the amount that came out. Then I dropped the pan...cleaned things up....changed the filter......and put the new filter in, installed the pan. I measured (as close as I could) the amount that came out when I dropped the pan.
Now you have a clean place to put the new fluid.....the pan is the sump from which the transmission pulls the fluid.
Then I added new fluid....flushed....added new fluid...flushed....and did that until I had gone through the amount of fluid that I used (I used 18 quarts). I added only about what I ran out each time.
I posted pictures.....including detail of the pesky filter gasket that wants to stay in the tranny....in my pictures at
http://community.webshots.com/album/201931518cScpNK