Do a pan drop and change the filter. Don't do a flush (especially a power flush that uses chemicals). You could do a "flush" using the cooler line letting the trucks pump do the work (several how to's online), but still do a pan drop.
As said, a 2000 may have a torque converter drain plug, makes it easy to get most all the fluid out at once without "flushing" it.
I installed a drain plug in mine, wish I had gone with the Dorman pan, only like $25 on amazon, and no chance of it leaking like installing a drain plug yourself. Mine does not have a torque converter plug, so I have done several drain and fills after I did the initial filter change. AS said above, with a drain plug, it is a quick thing to do a drain and fill (I will do it every 10,000 miles, it gets 4 qts out of ~14 qts in the system). I keep debating installing an inline filter.
You don't mention if you have the 4R70W or 4R100. Both can use Mercon V though (4R100 originally spec'ed for Mercon, but there is no licensed Mercon fluid anymore, and it has been back spec'ed for it).
Amazon has Havoline Mercon V for around $45 sometimes for 12 qts, as well as Supertech Mercon V for $4.27/qt at Walmart. First change I used the Supertech Mercon V, the last 3 I have used Maxlife. I have also used Maxlife in my BIL F150.
Some have issue with Maxlife being too thin (5.9 cSt @ 100°C) compared to Mercon V (7.5 cSt @ 100°C), but seems I had read that Mercon V shears quickly to lower than what Maxlife is, and Maxlife is more sheer stable.